The first two default colors (pale teal and pale purple) for the history graph card can be very hard to distinguish with red-green color vision deficiency (CVD, a.k.a. "colorblindness). Red–green CVD affects up to 8% of males and 0.5% of females of Northern European descent (Color blindness - Wikipedia), so odds are that a significant number of other HA users have this same issue.
Forum post 2021.7 History graph color changes requested the ability to change the graph colors, but even a global toggle to a secondary color palette would be a game changer for me.
