Why is the color picker for a diffuse material sometimes there, sometimes not?

Basically this:

I have yet to find the difference of those two projects and what I need to switch on/off.

Any help?

Click that fat “shipHullMaterial” bar. It toggles on/off.

That’s a nice feature in the full inspector – you can click anything to collapse it and save space. And those settings are saved. So if you toggle a rigidbody closed somewhere, the system remembers “rigidbodys are collapsed.” Everything else you select will be that way (until you click it again.) That’s usually what you want.

So, if you’re toggled a Material once. All Materials are shut. The funny thing is, it happens even in Assets (as you have there) where it makes no sense to ever hide it (but it uses the same Material-Display-tool, so it does.)