I'm not sure what you mean. They're just throwing each basic colour (values 0..255) onto its appropriate byte in a number (B lowest, G next, R highest), like this (apostrophes separate bytes for clarity, each character is a bit):
RRRRRRRR'GGGGGGGG'BBBBBBBB
However... this is not a normal language, but this Lua thing, so the little code can as well launch a space probe to the orbit or do laundry for aunt Helen, no one knows 😉
