Gradient Colorize Weirdness

Does anyone know what would cause the Gradient Colorize filter to not work properly?
I just want to make a simple color ramp on a rectangle object. This is my steps so far:

1. Make a rectangle with Rectangle Tool
2. apply the Gradient Colorize Filter to it
3. Adjust the Gradient

The problem is that the gradient does not apply to the shape.
Instead, a random color FROM the gradient is applied.
If I change the "Repeats" value, then I get a different color FROM my gradient.

It seems like this should work.

Do I need to start with a gradient on the shape before I apply the filter?

The "filter" doesn't really work on drawn objects much, you'd want to apply it to the Group that object is in. But that effects other stuff inside that Group...
But there is a much easier way to do this!
Change the Fill Mode to Gradient on the rectangle itself.

Ah. Of course.
I don't know why I didn't think of that. That was worth some Karma.

Thank you.