Basically you can create any colour from a combination of Red, Green, and Blue (hence the abbreviation RGB)
0 means a lack of that colour, and 255 is the strongest intensity. so 255,0,0 will be pure Red.
For Black...you have 0,0,0
for White, you combine all the colours equally strong 255,255,255
for dark Grey to light Grey, you use the same number for each.... 128,128,128 being mid grey.
There are some standard numbers for common colours...for example type RGB yellow in google and many sites will pop up.
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