change timeline color based on color mode

[Rperry2174]

Currently light color mode works pretty well for traditional css items. However, for the timeline, these colors currently don't change based on color mode and we should make it so that we're able to change these colors via color mode as well:

For example the yellow bars, should be a different color in light mode

also on this page

• red
• green
• blue
• pink

should all be better suited for light mode