profiles: graphical: make dark blue color more readable

The default dark blue color was honestly unreadable on the PIE using urxvt. Most students do not configure their environment, but the default configuration should be usable for their everyday use.

Closes #37 (closed).

WARNING: I did not try out to create a VM from this branch (unfortunately I don't have enough disk space on my laptop), I only tested the color on my session on the PIE.

Here is a before/after example, it is not as obvious as IRL (especially with the sun/lights around you):