I made some gentle suggestions and they were rejected. I was a bit pissed at first and intended to fire the client. Over the weekend it occurred to me that due to the way we were introduced, he didn't actually know that I have decades of experience making tool and device UI's [1] and probably thinks I am the software equivalent of a carpenter - not an architect.

I want to let him know in the nicest way possible, that he can take advantage of my decades of design experience to improve his UX without actually telling him "your design looks like ass". :-) Thoughts?

The area if the screen we're talking about is roughly 2" wide x 3 high - not a lot of room. His design isn't horrible but has some issues, namely:

4 different shades of blue, 5 if you count the background.

2 different fonts, one of which is a 7 segment display font

I suggested a single shade of blue, and a single font, cleaned up some stuff and made the readouts larger.

[1] Oscilloscope, CAD/CAM, laser controls, etc.