You're reading that backwards. For every skin you have to unlock the first color first.
So it's actually "you unlocked this artifact variant through organized raiding, here are some OTHER pve related achievements to get new colors for it".
And the point made at the very beginning of this topic still stands: Normal is so easy my dog could pug it and succeed. If you're not doing normal, it's because you DON'T WANT TO, therefore you should not get rewards. LFR is tourist mode, I'm glad they added tier sets back to it, but that where it ends.