It’s hard to get a good shot of the whole thing when it’s long and thin. The focus isn’t great and I had to change the setting on the iPad to even out the lights and darks.  

I think I’ve managed to spread out the colours pretty well. Each time I add a square, I’m mostly just looking at the adjacent squares to make sure they aren’t the same and show good contrast. 

Here’s a close-up.

  
Thirty four squares so far, so about 15% done.