Improve Default Plot Line Colors

[jamesdoyle21]

This is a known problem that has come up before. Sometimes the line colors on the plots in OM3 are too similar to tell apart. We need to either:

1. Improve the default plot line colors (set a default list perhaps so the first line plotted is always blue, second red, third green, etc)
2. Allow the user to customize line colors

[mpiannucci]

See Allow User to Customize Observation Drawer Plot Colors