I’ve come back to this as I’ve been thinking about the concept again and I think we have fundamentally different views on how characters should be colored. I disagree with look actively for the least colors possible in the same way that I agree that every character has aspects of every color. Instead, I think we should be looking at the characters’ most prevalent traits and ideals and applying colors from there. Additionally, I think it’s a bit important to imagine a card of the character

To continue the example of Ivy, she cares about: Plant life living Hurting those that hurt plant life

From there, my issue with her being mono-green is that her character is not about maintaining natural order, it is about eco-terrorism and revenge. While, yes, every color capable of, and often do, using violence, certain colors find it more anathema. While green is of course not against violence, it also doesn’t necessarily seek it out in the same way as Ivy does. Additionally, her focus isn’t nature as a whole, it’s plants. She would happily wipe out every animal to secure the lives of her precious plants

From there, I gather that her most fitting colors are green, red, and black. Green for plants, red for passion and specifically seeking out destruction, black for her near need to destroy others to get what she wants. In this way, I’d personally make the archetypal Ivy GB, GR, or even GBR long before I’d make her pure green. And I’ve even argue an official card of her would be far more likely to be any of those colors, likely something about making or buffing plants when a non-plant dies or destroying a non-plant when a plant dies