Because Spaces & Banners are limited in their colors (and very muted), they are very, very hard to distinguish in dark mode. Both greens look nearly the same.
It would be ideal to go back to allowing users to create high-contrast colors of their own choosing as you can with statuses and list colors.
Otherwise, I freaking love Clickup but this is an issue for those who are visually impaired and / or have color blindness.