Note that the colors I chose in the code are just aliases: 'CRGB::AliceBlue' is the same as '0xF0F8FF" which is the hexadecimal code for that color (see here). In RGB code, it means Red = F0, Green = F8 and Blue = FF. Then if you want to choose your own colors, you can use a 'color picker' such as the one from Google. It'll give you the HEX codes for the colors you choose, and you just have to copy them in the tables of lines 14 and 15.