Ron:
It’s amazing how many shades of white you can find at the paint store.
Isn't that the truth,  most people think white is white...  
I should have and did know to double check,  but on this job I figured it didn't matter.  
Was Wrong,  Reinforced the thought that it will always be a color match no matter,  figure it in.

Figuring out how to do something you have never done is what makes a good challenge.