/lit/ - Literature

Anyone know any good mind-mapping software that allows you organise along an additional axis beyond the two-dimensional mind-map layout e.g. colour-coding the nodes but with more than one colour so each node can belong to multiple categories? See image if that's too wordy. I need to organise my writing ideas by 'parent' relations plus their direct connections to each other, but also by several categories of themes; some of the ideas belong to one theme, others belong to multiple themes. All the mind map freeware I can find so far either doesn't allow non-parent connections or, like Scapple (pic related), only allow the most rudimentary stylisation of each box so I can't e.g. use a gradient fill to denote the idea belonging to two different categories simultaneously by using colour.