HexToRGB

From WoWWiki

Takes a hex string (must be 6 char long!) and converts it to a RGB set (0-255)

local function HexToRGB(hex)
	local rhex, ghex, bhex = string.sub(hex, 1, 2), string.sub(hex, 3, 4), string.sub(hex, 5, 6)
	return tonumber(rhex, 16), tonumber(ghex, 16), tonumber(bhex, 16)
end

Alternative version

Takes a hex string (must be 3 or 6 chars long!) and converts it to a RGB set (0-255). If hex is invalid, return black (0,0,0).

local function HexToRGB(hex)
    local rhex, ghex, bhex
    if strlen(hex) == 6 then
        rhex, ghex, bhex = strmatch('([a-fA-F0-9]{2})([a-fA-F0-9]{2})([a-fA-F0-9]{2})', hex)
    elseif strlen(hex) == 3 then
        rhex, ghex, bhex = strmatch('([a-fA-F0-9])([a-fA-F0-9])([a-fA-F0-9])', hex)
        if rhex and ghex and bhex then
            rhex = rhex .. rhex
            ghex = ghex .. ghex
            bhex = bhex .. bhex
        end
    end
    if not (rhex and ghex and bhex) then
        return 0, 0, 0
    else
        return tonumber(rhex, 16), tonumber(ghex, 16), tonumber(bhex, 16)
    end
end