Check out example codes for "possible colors used for html". It will help you in understanding the concepts better.

Code Example 1

#FF0000 means FF worth of Red, and no Green or Blue. The result is RED.

#0000FF means no Red or Green, and FF worth of Blue. The result is BLUE.

#FFFF00 means FF worth of Red and Green, and Blue. The result is YELLOW.

#000000 means no Red, Green, or Blue. The result is BLACK.

#FFFFFF means full FF amounts of Red, Green, and Blue. The result is WHITE.

#FFEFD5 has high values for all colors, giving a light result: PAPAYAWHIP.
   (no, I don't know who thought up the color names.)

#556B2F has lower values for all colors, giving a darker result: DARKOLIVEGREEN.

 

Code Example 2

#FFEFD5 (PAPAYAWHIP)   and

#556B2F (DARKOLIVEGREEN)

...are not web safe colors. They would get shifted to

#FFFFCC (NOT PAPAYAWHIP)   and

#666633 (NOT DARKOLIVEGREEN)

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