Choosing the right paint color Part 2

I'm writing about paint right now because I'm dealing with this right now. This week I shopped with two customers to pick out paint. It's not easy. Have you ever chosen the perfect color for your walls, only to find out the paint chip did not look like the finished produce?  It's happend to me, and is a very common problem, so don't feel stupid if you've had this experience. 
Undertones:  one challenge is that the paint you pick may have undertones that will come through on a larger surface, or a surface in a different locaiton.  A co-worker of mine years ago had their new home painted beige.  After the job was done, all they saw was green!!  They had the whole home repainted. I had one customer who had picked out a beautiful grey.  I kept seeing "blue".  I checked with the store clerk, and sure enough, there were strong blue elelments in the paint mix.  Solution:  Check with the clerk if there are "undertones" that maybe you should be aware of.  More paint tips to come . . .