Re-tinting already mixed color
I just recently had SW tint some Cashmere low lustre with a match of BM's Imperial Gray. This is the third color down on the Night Mist/Gray Wisp/Raindance strip (the one that matches Restoration Hardware Silver Sage). I had gotten a sample of Raindance before and thought the color was perfect for my bath. However I knew that paint colors slightly darken when you get them in matte or low sheens. I thought Raindance might go too dark in a low lustre, so I got my gallon mixed in the next color up, Imperial Gray.
Now, I think the Imperial Gray might be too light, and I think I would prefer Raindance. I have only used a couple of brush-fulls out of the fresh paint can (virtually nothing), so could I bring it back to the store and get them to add the extra tint to make it a match of Raindance? I could live with the Imperial Gray, but I would really prefer Raindance.