How to distinguish between colors in Html language

Question

Like which color will be darker shade of gray?
And the answer is #252525
How i know this

Answer 1

I'm really confused about the directions this post seems to be going in, but random guess:

https://www.w3schools.com/colors/colors_picker.asp

Answer 2

you can think about any color as 3 colors red green blue rgb 00 00 00 if you know how color works you will make any color you want

Answer 3

well here is a site that can teach u about color , hope u enjoy it.....

http://net-informations.com/q/web/color-codes.html