Good morning. We are looking to paint the entire interior and exterior of our new house in plaster.
The desired look is the colored, off-white, great variation plaster that is common throughout Europe. See two inspiration pictures attached.

We are having trouble understanding how color is applied to the plaster. When I spoke with a representative behind one maker of plaster (Diamond Plaster), they said the only way they knew of was to let the uncolored plaster fully dry, then paint over it with the desired color. It's our understanding that there is a better, more traditional approach where the color is added directly to the plaster, and then applied all at once.

Any and all help would be greatly appreciated. This seems to be somewhat rare in the US, so we are struggling to understand what technique is required, and even who can be hired (around Boston) who has experience in this area.

Thanks in advance!