Feature request: color per type of input / output

[tammojan]

In our rather complex workflow, we have three types of outputs (strings, data sets, solution sets). It would help a lot for the visualization if each of those would be represented differently, for example by using a different color.

The color could be based on the type (to distinguish strings from files) or ideally also on the file type (I'm not too familiar yet with CWL, so I'm not sure if the file type is stored).

[tammojan]

As an example, I'd like to achieve something like the following without all the brushing up in Inkscape that I now did. The colors here are actually distinct for each format.