[Kanegasi]

Don't worry, you're fine. I wasn't attacking you, just informing you. You don't need UnitGUID to get a player's GUID from chat, it comes in the 12th argument in chat event payloads. It's how that cvar I mentioned works in the UI code.

function ChatClassColorOverrideShown()
    local value = GetCVar("chatClassColorOverride");
    if value == "0" then
        return true;
    elseif value == "1" then
        return false;
    else
        return nil;
    end
end
 
function Chat_ShouldColorChatByClass(chatTypeInfo)
    local override = ChatClassColorOverrideShown();
    local colorByClass = chatTypeInfo and chatTypeInfo.colorNameByClass;
    return override or (override == nil and colorByClass);
end
 
function GetColoredName(event, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12)
-- truncate...
    if ( arg12 and info and Chat_ShouldColorChatByClass(info) ) then
        local localizedClass, englishClass, localizedRace, englishRace, sex = GetPlayerInfoByGUID(arg12)
 
        if ( englishClass ) then
            local classColorTable = RAID_CLASS_COLORS[englishClass];
            if ( not classColorTable ) then
                return arg2;
            end
            return string.format("\124cff%.2x%.2x%.2x", classColorTable.r*255, classColorTable.g*255, classColorTable.b*255)..arg2.."\124r"
        end
    end
-- truncate...
end

GetColoredName is called every single time ChatFrame_MessageEventHandler is called. Also, as long as any event gives you the GUID, it will return usable values, no matter who the player is. It's a universal solution for every player your UI interacts with. You're right about the cache thing, but there's no point in asking for info about an offline player or a player you don't see anywhere in the UI anyways.