I have a lot of difficulty telling whether or not I have selected a vote on CS stack exchange. The difficult is probably magnified by color blindness (Deuteranomaly, affects 5% of men).
It's hard to establish whether or not the contrast is "too low" in an objective manner. In terms of brightness contrast, WebAIM gives only 1.10:1 (with 3:1 as a recommendation for foreground/background large print contrast).
A color more like this
is much easier to distinguish and I think still "on-brand". (WebAIM gives it a brightness contrast ratio of 2.01:1).
Is there any hope the style can be adjusted to be clearer?