Plot curve colours should carry on from the last selected colour

[NickDraper]

From Richard Heenan:

If change the colour of the last workspace on a plot, then the next workspace added does get the next colour in the table as expected, but add any more added all get the same colour as the one before. Also, thank you for moving the invisible yellow colour further down the list.

[NickDraper]

This issue was originally trac ticket 6980