Use CSS variables in getColor

[jadebuckwalter]

Instead of hard-coding colors, use CSS variables so that grades are
more visible in dark mode.

[jadebuckwalter]

This fixes the original issue. But in the process I came across lightColors - what is that used for, and should those colors get CSS variables as well?

[psvenk]

This fixes the original issue. But in the process I came across lightColors - what is that used for, and should those colors get CSS variables as well?

Apparently this was added in a43af60 but it seems that it was not used at all then and is not used now, so I think it can be safely deleted (along with getLightColor).

[psvenk]

This mostly looks good, but I think it would be good to have a separate color (dark orange?) for D-range grades, both for maintaining consistency (every other letter grade has its own color) and because we shouldn't use red for a D when it is still a passing grade.

[psvenk]

Should be ready to squash and merge.

[psvenk]

Actually, I (semi-)retract my approval. I think it may be a good idea to compute the color first (using the variable), given that the color (as returned by getColor) will be entered into the JSON export and therefore should be portable.

This would involve re-computing all colors upon switching themes, which might be a little much. @jadebuckwalter Your thoughts?

[psvenk]

Or, we could keep using CSS variables within currentTableData and just make sure that we do not remove any variables in the future to maintain backwards compatibility. This breaks forwards compatibility, but we never guaranteed forwards compatibility in the first place. It would also be good to change green to var(--green) inside newAssignment in buttonFunctions.js.

[psvenk]

Sorry for the repeated comments. After 3f2819c, I think the status quo with the backwards-compatibility guarantee is the way to go, given that it's the least disruptive solution. @jadebuckwalter, feel free to squash-and-merge if you agree.