When you’re picking a color scheme (from the “Colors / Settings” button at the top of your Protopage), a new type of color picker is now available.
If the “Restrict to harmonious colors” option is not ticked, then you will be able to choose any possible color. This gives you the freedom to pick bright and vivid colors.
However, that freedom can come at the cost of text being unreadable on some hue variants of the color you have picked.
If you tick the “Restrict to harmonious colors” option, this will assist you in choosing colors where text is readable on all hue variants of that color.
This is particularly useful if you are making use of many different hues in order to color-code the tabs in your Protopage.