2 Photo Paint questions

Hi, I don't use Photo Paint nearly as much as Draw, so I'm still becoming familiar with all the features. The two issues I'm having today are:

1. Is there a way to change the color of a brush mask? I'm working with an image that is all shades of red, and the default red mask makes it nearly impossible to see what I'm doing. If there was a way to change the mask color to maybe green it would be a lot easier to see.

2. The property of my mask tool seems to be changing back and forth any I haven't changed any settings. Sometimes I can click with the magic wand on different areas of the image and add to the mask as I please. Then all of a sudden I can't do it without holding the shift key. Clicking a new area removes the previous area mask. Am I inadvertently changing a setting somehow?

Thanks for your help,

Neil