Tools for learn RGB css colors?

Answer 1

https://www.w3schools.com/colors/colors_picker.asp
https://www.w3schools.com/cssref/css_colors.asp
https://coding.smashingmagazine.com/2012/10/the-code-side-of-color/

Answer 2

Red Green Blue
xx xx xx
x is a hexadecimal value (0 to F)
not much more to it besides experimentation ;)

Answer 3

few helpful links of online tools I use for picking colors in the code itself
https://code.sololearn.com/W5Of8safsGpc/?ref=app

Answer 4

In RGB each color is represented by a number 0 - 255. 256 positions. That's 2^8. In Hex there are 16 numbers 0-F. To get 256 we need 2 hex decimals. 16×16=256.
So for red The RGB is 255, 0, 0.
In hex that is FF (16x16=256, but it starts at 0 so 255). 00 is 0 for G and 00 is 0 for B.
00 = 0
01 = 1
0A = 11
1F = 16 etc
So when you look at a hex you probably won't know the exact color but you can guess because you'll know the relative amounts of r g and b. Practice with a color wheel in your favorite graphics software or on a website to see what the different combinations do.