Note that some weird cards (especially old ones) aren't actually useful, even though they technically 'do' something, though I do share your fascination.
Well Laid Plans won't work, the creatures are colorless, they have
no colors to share. This is the reason that
invoke prejudice _does_ work.
Also, consider that you still need to pay the appropriate color to cast the spell, it's just colorless once it's on the battlefield. So
Chaos Moon won't give anything +1 or -1, it could double the amount your mountains make, but when it turns your mountains to produce colorless mana, you won't be able to cast
Goblin Welder anyway. (PS, am I missing something? It looks to me like
Goblin Welder exchanges artifacts, removes 1 and adds 1, keeping the count even or odd, not changing it.)
When you're looking at a weird card like this, you're probably best off starting by looking for creatures that have a drawback having to do with what the card changes. Are there any creatures that care about sharing colors? Do any of those 'break' when it can't ever share a color?
Fear and Intimidate get much better, since now only artifact creatures can block them. Maybe this could be used as sideboard tech in an intimidate deck vs same color matchups.