Dr Darren says "Use B/W and coloured pen only for exceptional states and/or test results"

The more I work with UML and SysML the more convinced I am of this, even if it is a contentious view.
And you will find that throughout this eSchool I apply this principle more often than not.

PROS of using black pen and no fill include:

1. reduces arbitrary bias that has no place in engineering and can even be dangerous
2. prints better
3. emphasises UML over a particular tool's colour scheme, and thus appeals better to the wider UML community
4. provides a suitable background for coloured states like: ERROR (I use red pen) and ISSUE (I use orange pen) and OK (I use green pen)
5. black and white DOES reduce the noise in your head and DOES help you to concentrate on content (engineering) rather than cosmetics

In particular, I recommend that you do not work with the default MagicDraw UML colour styles for serious engineering, even though many customers are used to them:

1. the MagicDraw UML colours are completely arbitrary, and they promote arbitrary colour associations.
2. using the MagicDraw UML colours (or other colour schemes will strong fill and pen style) makes it much harder to use coloured pens to indicate states like ERROR and ISSUE.

Again, these are my opinions, not those of No Magic or the MagicDraw developers, so please do use whatever works for you.