I'm just now reading about gradients, and I'm trying to create a gradient on a box where it's blue on the right and red on the left (wth the blended violet in the middle). I know gradient is mostly used for special effects, but I just want gradient colors on a box.

I tried every mode in the gradient window (incidence, bump, all of them). All I get is a solid color.

How do I apply an actual color gradient left to right on a simple box shape?