Update node on property change?

I have a FloatVectorProperty to store a RGB color.

When the FloatVectorProperty is changed in the panel UI I’d like it to change a node’s color.

How is this done?

I believe what I was looking for was

def update_func(self, context):
    print("my test function", self)

bpy.types.Scene.testprop = bpy.props.FloatProperty(update=update_func)