Fix color contrast issues

[bedmison]

Address any color contrast issues that are found. Color contrasts are measured between foreground and background colors. The standard contrast ratio we want to maintain is at least 4.5:1.

The WebAIM Contrast Calculator is an easy-to-use widget for finding the contrast ratio.

Work from https://codeworkoutdev.cs.vt.edu/gym/exercises . It shares much of the same theming as OpenDSA-LTI. For each element, test the contrast ratio. If it is less than 4.5, work out a color combination that gets us to the 4.5 level. Once you figure out that combination, record the changes you make as a note attached to this issue. Record the element, any CSS selectors you changed, and the new colors.

Remember, you aren't working from source code, so the changes you make will be lost when the page refreshes. That's why it's vital to record the changes here.

[yoonwoo1000]

I reviewed the foreground-background color contrast based on WCAG 2.1 AA standards (minimum 4.5:1 contrast ratio for normal text). See full color list in attached PDF.

color contrast.pdf

[cashaffer]

YoonWoo -- Thanks for getting this documentation started! I have created a working version in the form of a Google Doc that we can build on: https://docs.google.com/document/d/1_90r3ceN79t2seSSpSVnGry5uD4O7-SihRFwHmzlcCk/edit?usp=sharing