Add colors

[kevinburke]

It'll be tricky to do this in a way that's not terrifying. Ideas:

• Color the input borders, either by type (dict, list etc) or by depth (first level, 2nd level etc). Depth feels more useful as the visual layout is already a cue for which type of element exists.
• Draw vertical color lines to indicate which groups belong together. For example, on the example page, a colored line would go between the "teams" input and the "Add new object" button.
• Shade the backgrounds with a light color, but this sounds horrifying as well. Maybe only filling in the deepest level, then filling in all keys with the same value, could work.

I'll try to mock out some ideas and post them here.