No alt text for button icons

[mlamond]

Describe the bug
There is no visible alt text for icons (color switch, sliders, eyedropper, question mark.) I wasn't sure what these were for until clicked.

Desktop (please complete the following information):

• OS: [e.g. Windows 8 64 bits]
• Version [e.g. 1.1.1]

To Reproduce
Hover over any of the button icons

Expected behavior
alt text describing what this button does

Screenshots
If applicable, add screenshots to help explain your problem.

Additional context
Add any other context about the problem here.