Hello all, Can we flip the gradient colour by expression control.

It depends on what you want to do. There is expression color control for a gradient, but you can point one gradient to another using a simple pickwhip. You can tie the start and endpoints of a gradient to any other position property, you just have to compensate for the comp position of the layer or shape the layer has been applied to.

A clear explanation of what you are trying to accomplish would help us point you in the right direction. I have no idea what Flip the gradient colour means. If it's just flopping the start and end point, that is pretty easy to do, but the points need to be tied to something as a reference like shape layer Rectangle size, or sourceRectAtTime, or an expression control, or another gradient.