Elements must have sufficient color contrast for usermanagement

**[Original report](https://bitbucket.org/laborstudents/cas-flask/issue/315) by Jamal Aw Yonis (Bitbucket: [awyoonisj](https://bitbucket.org/awyoonisj), GitHub: [jawyoonis](https://github.com/jawyoonis)).**

----------------------------------------

**Issue description**:

Ensures the contrast between foreground and background colors meets WCAG 2 AA contrast ratio thresholds. The color contras should be at least **4:5:1** rotion for small text and** 3:1** for large text. To learn more about the issue GO TO THIS [ LINK ](https://dequeuniversity.com/rules/axe/3.1/color-contrast?application=AxeChrome)

Files effected: usermanagement.html/js/css