That's a very good point about colorblindness. I plan to mostly show congestion with animated sprites. Small people will travel along the logistics paths, based on how many items are being transmitted. Their speed will be based on congestion, travelling visibly slower in congested areas.
There will probably be an option for a color coded overlay, and I'll try to take colorblindness into account.
Please feel free to make any other accessibility suggestions, I would find them very useful.