How to ensure the child controls like a label in a tab page get the same themed-gradient backcolor as the tab page?

Ensure the child controls in tab page

Make the child control transparent. In a label, you can do this by setting its FlatStyle to Standard and backcolor to Transparent.

A limitation with this approach that is to be noted is that child controls themselves cannot be drawn themed when using this approach (setting their background to transparent). For example, to make a check box’s background transparent, you have to set its FlatStyle to Standard (not System) which will only give it a non-themed look.

The above inability to draw transparent-themed child controls is an issue in the platform sdk that has been reported to Microsoft.