The colors look like a nice pick. I like how you did the expressions. However, the dialogue text looks a little bit small for reading. Maybe you could have made some of the words in bold, to help your joke along?

I feel that you didn't use your space very wisely in the first two panels, having too much empty space at the top.

Otherwise, this is fine. I'm good with you using flat colors for this, and doing a vague blurry background, to keep it all simple.