I've also used a plain back so the thread will be visible from the back as well. It should form its own picture.
I've sampled a few different types of thread.
I tried a polyester (so fine) but it split constantly. The reason I tried to use it is that it was the right color.
So I'm back to the tried and tested superior 50 weight cotton thread.
Now things have changed. This thread is now 3 ply and it's a little thicker than the 2 ply I've used in the past... it's now equal in size to the Aurifil which I will use in combination.
Just looking at the thread and placing it on the image, it's impossible to see if its going to be the correct color.
So in reality you need to sample.
To date, I've worked for an hour on two colors.
It really is just like drawing.