Unity panel with border radius and a solid color

Hey,

I’m new to Unity3D and I’d like to create a panel with a white solid background and a 30px border radius in the top left edge and bottom right edge.
I’ve created a panel and added the source image to the panel:
41648-uipanel.png

It contains the correct form and the correct background color. However, it only appears the correct form but the background color remains grey with a alpha transparency:

So Unity3D seems to only add the look but not the color. If I assign a white material it will delete the border radius.

How can I add a solid white color background to my panel if it has a border radius?

Select the panel, in Inspector under Source Image you can find a Color property. Select it and change the alpha (A) value from 100 to 255.