I've used Photoshop 15 for years now. Recently when adding a frame to a photo, I chose the color red, but the frame only comes out black?
Restore default preferences
Preference settings control how Photoshop Elements Editor displays images, cursors, and transparencies, saves files, uses plug‑ins and scratch disks, and so on. If the application exhibits unexpected behavior, the preferences file could be damaged. You can restore all preferences to their defaults.
Note: Deleting the preferences file is an action that cannot be undone.
Do one of the following:
Press and hold Alt+Control+Shift (Mac: Option+Command+Shift) immediately after Photoshop Elements begins launching. Click Yes to delete the Adobe Photoshop Elements settings file.
Go to Edit > Preferences (Mac: Photoshop Elements > Preferences > General), click the Reset Preferences on next launch button, and then click OK. When you restart Adobe Photoshop Elements, all preferences are reset to default settings.
A new preferences file is created the next time you start Photoshop Elements Editor. For information on a specific preference option, search for the preference name in Help.
If Peru Bob's advice doesn't work for you, what OS and version of Elements are you using?
How are you trying to add the frame? Do you mean you are applying a Stroke to a selection?
Is the image in Greyscale Mode (Black and White photo)?
If the image is in Greyscale mode, you need to change it to RGB in the Image>Mode menu. This will not change the B&W image. But it will allow you to apply a colored stroke.