how to highlight/shade a segment in an image.

[Brickle Macho]

I over segment an image using a superpixel algorithm.   I region grow
using the superpixels to end up with a segmented image, a label-image.
I overlay the label boundaries using mark_boundaries().   I can click on
a segment/region and indicate it as either foreground or background.
This foreground/background information is maintained in a python dict.
How can I provide visual feedback, say tinting the clicked segment, in
the image.

Short version, given a label, a lable-image and a image, how do I
shade/tint the label area.

Thanks,

Michael.
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