misc: set color scheme

[ruben-arts]

Putting in a first pass on generalizing the colors used in the terminal.

[baszalmstra]

You can put the style function into constants (e.g. in the consts module?). That makes them easy to reuse and change later.

[baszalmstra]

Mmm now that I think of it, we could also do this through the different struct names. A Feature::name() returns a FeatureName we can add a function: fancy_display() that returns the styled object? If we then remove the Display from FeatureName a user is forced to either call as_str() or fancy_display() to print it. WDYT?

[ruben-arts]

So that fancy_display for TaskName required a lot of refactoring. Butttt this does make sense to me.