Kathy, I said white just in case your photo wasn't covering the whole photo, you mentioned the mask was showing through. It really doesn't matter what color it is unless some is showing through because the photo is smaller than than the mask. You could also enlarge the photo to rid yourself more of the black you don't want. You could use this technique in the future when your photo won't cover the whole mask and choose a color suitable to your background or color in your photo.
As for changing the mask color. I didn't see what PSE you were using. But I think you are using a brush as the mask? (It looked like one of the Junk in the Trunk Brushes, I could be wrong) If so, just make sure your fore color is white or the light color of your background then use the brush again to make another one. If you aren't using a brush then add a blank layer between the photomask and the photo and fill it with one of those light colors.
I always use my Background Blender Brushes
and Mari J mentioned Syndee's Painted Brushes
. You choose which is best for you, but those are good ones.
Hang in there, you will get it! It took me a lot of time to develop my own style too.