Web styles not working

What would cause a web style to not update in the browser?

For example, I have a rectangle in a window and on the mouseup event:

me.style = BlueBG

BlueBG is super simple, the background property is the only property and it is set to 255 for blue. The style is set, but the rectangle never changes color… Why?

If I set it to a style that changes its corner radii, those update, but the color will not change…
Any thoughts?

You need to assign a style to the rectangle within the IDE and then change it on the mouseup event. It won’t work if the rectangle hasn’t been initiated with a style - (from my experience).