2nd Rainbow

I have finally got around to going back and having another go at shading through a rainbow. This time I used two shades of each colour to try to get better matches when changing colours. Here is the outcome:

Green to yellow is still a problem. The only way to do it effectively seems to be to pick very light colours but then the pattern doesn't show up. Also, by sorting the transition between yellow and orange the problem has simply been moved along a bit to red/orange. Possibly it could be done if I bought a set of colours specifically rather than relying on what I already have but I'm not sure. I think to have a truly smooth transition you would have to use too many thread colours for it to be practical. But do the transitions have to be smooth? In most practical situations, rather than these shading experiments, you would want a change in colours to be noticeable. I'll have to think some more.