Green as a colour tends to favour natural, organically developing solutions to problems. In-game, it's very anti-technology/anti-artifice, having a large number of cards that wreck or interfere with artifacts. Its enemies are blue (due to its obsession with artificial solutions and valuing of reason over instinct) and black (on account of its all-for-one mentality, which clashes with green's one-for-all outlook).
I'm interested to hear how that lines up with your characters' philosophies.
Apologies that it's taken me so long to reply to this, I've been at a music festival drinking lots and singing loudly.
I chose green for Kala as despite her Sebiestor roots and natural affinity for tinkering, her family work in agriculture. This has left her with a tendency to take the long view and just let things develop (although, capsuleerhood has somewhat ruined this as everything happens
so fast in relative terms).
Her own personal goals, not those of her tribe and/or family, are based almost purely around her own independence and freedom. Of the colours I picked, Green and Red, the most applicable sections of these are the first half (going anti-clockwise) of each; Independence and Impulse and their subsets; Nature, Growth, Freedom and Action.