The other thing that I played about with was the mix of ink. I put two colours on the ink stone and rolled them together on the plate. This created an interesting blend.
I discovered that it's easier to print light colours than black (or at least, the imperfections are not so obvious when printing with light, bright colours on white paper).
Here are a couple of examples, side by side, with different weights of ink and different blends of light grey and light blue.