Adopt design color palette for all text headers #159

Description

On many (all?) pages with text headers, we appear to adopt a grey color (e.g. text-forecolor, text-heading) that appears too faint.

Steps to Reproduce

1. Log in
2. Inspect the headers ("Instructing" and "Attending")

Expected vs Actual

Expected:

These headers should adopt the highlight color from the graphic design color palette: #f8eedf

Actual:

Instead, we're getting faint grey, such as the following screenshots that use #757575 or similar shades that I believe are defaults that came with toastify

Screenshots / Logs

Additional Context

Some content (non-headers) use text-white which is acceptable contrast, but the headers need to be updated to consistently use #f8eedf