Is that even possible?
How to change the corner radius of a color-rect?
I do not think so, not with a ColorRect node. You can use a Panel node with a custom flat-style panel texture, set the color to white and the corner radius to what you want, and then use self_modulate
to change/tint the panel to whatever color you need.
7 months later
@TwistedTwigleg you're right, using a Panel is exactly what I needed!