In order to maximize the odds of having a web page look the same on different monitors and different browsers, we are limited to 216 colours on the Web. This is because each operating system reserves some colours for itself, and the two don't reserve the same colours. UNIX is an entirely different breed.

Moreover the same colour will appear different to different people, because colour is literally in the eye of the beholder. And about 8% of the male population suffers some degree of "colour blindness."

Each colour below contains the hexadecimal values and the RGB (Red, Green, Blue) Values.
Select a colour and copy & paste the hexadecimal value into your HTML document.

The 216-color web palette was once the standard for using color on the web. This palette is a set of colours created by Netscape that looks the same on all web browsers and Windows / Macintosh platforms:

The idea behind the palette was a great one -- since colours do not display the same on different kinds of computers, let alone different browsers, limit the use of colours to only those that did appear the same no matter what they were shown on.
 
Using colours other than the ones shown above dither unpredictably. Dithering means that the browser would attempt to simulate the colour it couldn't display by showing small pixels of the closest colours. If the image used a peach-flesh tone which the browser could not display, the browser would dither that using pink, yellow, and orange from the web palette, creating a speckled effect. These images would, understandably, look less than polished.
 
Unfortunately, the 216 palette is, well... ugly. It really is. The colours it contains are very restricting design-wise. There was a time when I embraced it wholeheartedly, an HTML purist who believed that you should always use the 216 colour palette and nothing else. It was also a time when most people were running Windows 3.1 with Netscape 2.0 and had video cards that could display 256 colours... or even less than that. Making non-dithering images was very important.
 
These days, almost everyone has a display that can show at least 256 colours. Most new computers can display 16 million colours.   It's hard not to want to take advantage of using some of them, isn't it?
 
However, when you begin using colours outside the 216 colour web palette, you move into a gray area where you will not know exactly what shades of colours your users are seeing. As developers, we like to have the best tools that money can buy, and if you've invested well in a quality video card and monitor, you can be relatively certain that what you are creating is what your users are seeing.
 
Or can you? A lot of your users have cheap monitors. Your users have video cards that can't render the wide variety of colour subtleties that yours is able to. Perhaps you have a less-than-optimal hardware setup yourself. How will you know what your user is going to see? We haven't even mentioned that they're using a different web browser than you, and they're using a Mac, PC, or even their television to surf the web. Different devices cause different gamma shifts in colour.
 
 

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Original image   Gamma shift (light)   Gamma shift (dark)
 
Gamma involves many elements, but it can be summarized as the relationships between light and dark areas on the screen. Images created on Macintoshes without gamma correction can look very dark on PCs. So, what do we do? Ultimately, we have to try to create something that's going to look acceptable on all platforms. Previewing your work on several computers with different monitors, video cards, browsers, and operating systems will help you see if the site looks acceptable.
 
I said before that I used to be a tried-and-true "only use the 216 web palette" devotee. I'm somewhere in the middle now. The web palette does not work for photographs. It just doesn't render them in a visually acceptable manner.
 
There's also the client issue. Your clients are going to demand the use of certain colours. If their logo is a bright purple that doesn't match up to one of the colours in the web palette, you're probably not going to be able to convince them that they need to change it..!
 
My rule of thumb is to use the web palette when you can.
 
Summary:
   
Use the web palette when you can.
   
Consider gamma shifts when choosing and rendering colour.
   
Preview your work on several computers with different setups to see if it looks acceptable
 

Example:

   
Hexadecimal Value

RGB Color Code

 

 

#FFFFFF

R=255

 

G=255

 

B=255

#FFFFFF

R=255
G=255
B=255
#FFFFCC

R=255
G=255
B=204
#FFFF99

R=255
G=255
B=153
#FFFF66

R=255
G=255
B=102
#FFFF33

R=255
G=255
B=51
#FFFF00

R=255
G=255
B=0
#FFCCFF

R=255
G=204
B=255
#FFCCCC

R=255
G=204
B=204
#FFCC99

R=255
G=204
B=153
#FFCC66

R=255
G=204
B=102
#FFCC33

R=255
G=204
B=51
#FFCC00

R=255
G=204
B=0
#FF99FF

R=255
G=153
B=255
#FF99CC

R=255
G=153
B=204
#FF9999

R=255
G=153
B=153
#FF9966

R=255
G=153
B=102
#FF9933

R=255
G=153
B=51
#FF9900

R=255
G=153
B=0
#FF66FF

R=255
G=102
B=255
#FF66CC

R=255
G=102
B=204
#FF6699

R=255
G=102
B=153
#FF6666

R=255
G=102
B=102
#FF6633

R=255
G=102
B=51
#FF6600

R=255
G=102
B=0
#FF33FF

R=255
G=51
B=255
#FF33CC

R=255
G=51
B=204
#FF3399

R=255
G=51
B=153
#FF3366

R=255
G=51
B=102
#FF3333

R=255
G=51
B=51
#FF3300

R=255
G=51
B=0
#FF00FF

R=255
G=0
B=255
#FF00CC

R=255
G=0
B=204
#FF0099

R=255
G=0
B=153
#FF0066

R=255
G=0
B=102
#FF0033

R=255
G=0
B=51
#FF0000

R=255
G=0
B=0
#CCFFFF

R=204
G=255
B=255
#CCFFCC

R=204
G=255
B=204
#CCFF99

R=204
G=255
B=153
#CCFF66

R=204
G=255
B=102
#CCFF33

R=204
G=255
B=51
#CCFF00

R=204
G=255
B=0
#CCCCFF

R=204
G=204
B=255
#CCCCCC

R=204
G=204
B=204
#CCCC99

R=204
G=204
B=153
#CCCC66

R=204
G=204
B=102
#CCCC33

R=204
G=204
B=51
#CCCC00

R=204
G=204
B=0
#CC99FF

R=204
G=153
B=255
#CC99CC

R=204
G=153
B=204
#CC9999

R=204
G=153
B=153
#CC9966

R=204
G=153
B=102
#CC9933

R=204
G=153
B=51
#CC9900

R=204
G=153
B=0
#CC66FF

R=204
G=102
B=255
#CC66CC

R=204
G=102
B=204
#CC6699

R=204
G=102
B=153
#CC6666

R=204
G=102
B=102
#CC6633

R=204
G=102
B=51
#CC6600

R=204
G=102
B=0
#CC33FF

R=204
G=51
B=255
#CC33CC

R=204
G=51
B=204
#CC3399

R=204
G=51
B=153
#CC3366

R=204
G=51
B=102
#CC3333

R=204
G=51
B=51
#CC3300

R=204
G=51
B=0
#CC00FF

R=204
G=0
B=255
#CC00CC

R=204
G=0
B=204
#CC0099

R=204
G=0
B=153
#CC0066

R=204
G=0
B=102
#CC0033

R=204
G=0
B=51
#CC0000

R=204
G=0
B=0
#99FFFF

R=153
G=255
B=255
#99FFCC

R=153
G=255
B=204
#99FF99

R=153
G=255
B=153
#99FF66

R=153
G=255
B=102
#99FF33

R=153
G=255
B=51
#99FF00

R=153
G=255
B=0
#99CCFF

R=153
G=204
B=255
#99CCCC

R=153
G=204
B=204
#99CC99

R=153
G=204
B=153
#99CC66

R=153
G=204
B=102
#99CC33

R=153
G=204
B=51
#99CC00

R=153
G=204
B=0
#9999FF

R=153
G=153
B=255
#9999CC

R=153
G=153
B=204
#999999

R=153
G=153
B=153
#999966

R=153
G=153
B=102
#999933

R=153
G=153
B=51
#999900

R=153
G=153
B=0
#9966FF

R=153
G=102
B=255
#9966CC

R=153
G=102
B=204
#996699

R=153
G=102
B=153
#996666

R=153
G=102
B=102
#996633

R=153
G=102
B=51
#996600

R=153
G=102
B=0
#9933FF

R=153
G=51
B=255
#9933CC

R=153
G=51
B=204
#993399

R=153
G=51
B=153
#993366

R=153
G=51
B=102
#993333

R=153
G=51
B=51
#993300

R=153
G=51
B=0
#9900FF

R=153
G=0
B=255
#9900CC

R=153
G=0
B=204
#990099

R=153
G=0
B=153
#990066

R=153
G=0
B=102
#990033

R=153
G=0
B=51
#990000

R=153
G=0
B=0
#66FFFF

R=102
G=255
B=255
#66FFCC

R=102
G=255
B=204
#66FF99

R=102
G=255
B=153
#66FF66

R=102
G=255
B=102
#66FF33

R=102
G=255
B=51
#66FF00

R=102
G=255
B=0
#66CCFF

R=102
G=204
B=255
#66CCCC

R=102
G=204
B=204
#66CC99

R=102
G=204
B=153
#66CC66

R=102
G=204
B=102
#66CC33

R=102
G=204
B=51
#66CC00

R=102
G=204
B=0
#6699FF

R=102
G=153
B=255
#6699CC

R=102
G=153
B=204
#669999

R=102
G=153
B=153
#669966

R=102
G=153
B=102
#669933

R=102
G=153
B=51
#669900

R=102
G=153
B=0
#6666FF

R=102
G=102
B=255
#6666CC

R=102
G=102
B=204
#666699

R=102
G=102
B=153
#666666

R=102
G=102
B=102
#666633

R=102
G=102
B=51
#666600

R=102
G=102
B=0
#6633FF

R=102
G=51
B=255
#6633CC

R=102
G=51
B=204
#663399

R=102
G=51
B=153
#663366

R=102
G=51
B=102
#663333

R=102
G=51
B=51
#663300

R=102
G=51
B=0
#6600FF

R=102
G=0
B=255
#6600CC

R=102
G=0
B=204
#660099

R=102
G=0
B=153
#660066

R=102
G=0
B=102
#660033

R=102
G=0
B=51
#660000

R=102
G=0
B=0
#33FFFF

R=51
G=255
B=255
#33FFCC

R=51
G=255
B=204
#33FF99

R=51
G=255
B=153
#33FF66

R=51
G=255
B=102
#33FF33

R=51
G=255
B=51
#33FF00

R=51
G=255
B=0
#33CCFF

R=51
G=204
B=255
#33CCCC

R=51
G=204
B=204
#33CC99

R=51
G=204
B=153
#33CC66

R=51
G=204
B=102
#33CC33

R=51
G=204
B=51
#33CC00

R=51
G=204
B=0
#3399FF

R=51
G=153
B=255
#3399CC

R=51
G=153
B=204
#339999

R=51
G=153
B=153
#339966

R=51
G=153
B=102
#339933

R=51
G=153
B=51
#339900

R=51
G=153
B=0
#3366FF

R=51
G=102
B=255
#3366CC

R=51
G=102
B=204
#336699

R=51
G=102
B=153
#336666

R=51
G=102
B=102
#336633

R=51
G=102
B=51
#336600

R=51
G=102
B=0
#3333FF

R=51
G=51
B=255
#3333CC

R=51
G=51
B=204
#333399

R=51
G=51
B=153
#333366

R=51
G=51
B=102
#333333

R=51
G=51
B=51
#333300

R=51
G=51
B=0
#3300FF

R=51
G=0
B=255
#3300CC

R=51
G=0
B=204
#330099

R=51
G=0
B=153
#330066

R=51
G=0
B=102
#330033

R=51
G=0
B=51
#330000

R=51
G=0
B=0
#00FFFF

R=0
G=255
B=255
#00FFCC

R=0
G=255
B=204
#00FF99

R=0
G=255
B=153
#00FF66

R=0
G=255
B=102
#00FF33

R=0
G=255
B=51
#00FF00

R=0
G=255
B=0
#00CCFF

R=0
G=204
B=255
#00CCCC

R=0
G=204
B=204
#00CC99

R=0
G=204
B=153
#00CC66

R=0
G=204
B=102
#00CC33

R=0
G=204
B=51
#00CC00

R=0
G=204
B=0
#0099FF

R=0
G=153
B=255
#0099CC

R=0
G=153
B=204
#009999

R=0
G=153
B=153
#009966

R=0
G=153
B=102
#009933

R=0
G=153
B=51
#009900

R=0
G=153
B=0
#0066FF

R=0
G=102
B=255
#0066CC

R=0
G=102
B=204
#006699

R=0
G=102
B=153
#006666

R=0
G=102
B=102
#006633

R=0
G=102
B=51
#006600

R=0
G=102
B=0
#0033FF

R=0
G=51
B=255
#0033CC

R=0
G=51
B=204
#003399

R=0
G=51
B=153
#003366

R=0
G=51
B=102
#003333

R=0
G=51
B=51
#003300

R=0
G=51
B=0
#0000FF

R=0
G=0
B=255
#0000CC

R=0
G=0
B=204
#000099

R=0
G=0
B=153
#000066

R=0
G=0
B=102
#000033

R=0
G=0
B=51
#000000

R=0
G=0
B=0