Increase contrast between relearning and learning cards in graphs

> image813×331 21.5 KB
> The new cards and re-learning cards are nearly the same color, and I really have to squint to tell the difference.
> In AnkiDroid, red was for forgotten cards and blue was for new cards. This was easy to read at a glance.

Originally reported on https://forums.ankiweb.net/t/the-color-coding-in-the-stats-is-hard-to-see/43911

Start with the attached graph image and the linked forum report to understand the contrast problem and the distinction between new and relearning cards. Locate the graph color configuration in the repository, then verify that the two card categories are distinguishable at a glance and that the graph remains readable.

Written by the indexing model from the issue text.