I've painted a patched, bare plaster wall with a medium purple claypaint (Earthborn, "Jack Horner" color). The few places where I've patched the wall the paint is significantly darker, even after a mist coat, a full coat, and two further goes at spot painting those areas. It seems to be an absorption issue, as each time the patched areas took far, far longer to dry than the areas around them. How can I remedy this?
Below is a photo I took a bit after spot painting one of the patched areas with a roller. The new paint directly on the patched cracks is still quite wet, while the paint to each side is nearer to being dry.