I have a universe: a list of "Systems", each with their own center, type and radius.

A small part of such a universe could look like this:

Systems:

• Can be very close to a different system, e.g. overlap
• Can be inside another, much bigger system
• Can be very far away from any other systems
• Spawn system specific entities and particles inside the system radius
• Have some properties like background color

So far so good. However, the player can fly around freely, inside and outside of systems, in real time.

How do I interpolate and determine things like the background color now, depending on camera position?

E.g. if you are halfway between a green and a red system you should see a background halfway between red and green, or if you are inside a lilac system near the center and at the border of a green system you should get a mostly lilac background etc.