Color format for things like PrimaryColour

[NOSDOOM]

I'm sure I'm missing something obvious but I can't figure out the format of the colors for things like "PrimaryColour" when you use getStyles or setStyles. I thought at first that they were just the hex color code converted to decimal, but when I converted "FFFFFF" to decimal I get "16777215" instead of -256 so I thought that was a special use case but when I tried red(FF0000) as "0000FF"(GBR format) I get 255 which also isn't right. So I'm wondering if I'm missing something, or there is a color reference somewhere, or maybe an easier way to change colors that I'm not seeing. Thank you.