The second bar of the attached shows two uses of the colour green, but they are different voices. Is this a bug, or does someone know how I achieved this by mistake? Thanks! David
Zoom in. They’re two different shades of green.
It’s perhaps and odd choice by Dorico but if you insist on using lots of NEW different voices (rather than just using V to reuse existing ones) then this is an inevitable consequence!
Thanks, pianoleo. I see now that they are slightly different; but I have to look very carefully! 
David
I think this HAS previously been discussed here, and the general consensus is that it would be nice if Dorico had a slightly broader colour palette.
You’ve used eight voices including the two in the bass staff, and in copying out your example I see that it’s impossible to use fewer than seven voices here.
Yes.I should have thought that the avoidance of intermediate green-blue colours might have been useful for those who are colour blind (which I am not).
After your earlier remark, I also managed to lose one voice. Being used to Sibelius, which allows four voices on each stave, as opposed to Dorico’s counting over both staves, I can see that the latter, while seemingly complicated, probably gets over the problem of cross stave notes that Sibelius had when I last looked.
David