Color is not quite right... again.

I have been using StickerMule for some time now, but recently, I have had two jobs with inaccurate color (both shirts). I have had other printed items (stickers and magnets with the same artwork) come out great, but the shirt process seems to be off. StickerMule was good enough to reprint one of the shirts, but I didn't bother with the second. I may just have to look elsewhere for shirts in the future.