WoWInterface - Mark of the Thunderlord giving me lua code probs

Hey Everyone!
I have this lua code I been using in WeakAuras that will grab the color in the display color box. And when the timer reaches the warning_time then it changes the color by grabbing the color in the animation color box.
So this code works for mostly for any buff or debuff but when I tried it for " Mark of the Thunderlord "
( the weapon enchant buff ) nothing happend. I asked around about it and was told that Blizzard made the buff unknown instead of player? I'm not sure what that means but it's keeping the lua code from working right on it.

I messed with the code a bit but so far I have been unlucky getting it to work for that one buff.
( " Mark of the Thunderlord " ) So does Anyone know what command might work instead and can explain to me why this one buff doesn't work with this lua code when the rest do?
I also wanted to point out if I check Own Only on the trigger for Thunderlord it won't even appear after. I have to keep it unchecked.

Code:

function(progress, r1, g1, b1, a1, r2, g2, b2, a2)

    -- Set the debuff and threshold time here:

    local debuff_name, warning_time = "Mark of the Thunderlord", 4

    

    local _,_,_,_,_,_,expires, etc = UnitAura("PLAYER", debuff_name,

    nil, "PLAYER|HELPFUL")

    if expires ~= nil then

        local time_left = expires - GetTime()

        if time_left < warning_time then

            return r2, g2, b2, a2

        end

    end

    return r1,g1,b1, a1

end