Messing around, I discovered that Pixelmator Pro is changing brushed colors in a bad way. I can't quite figure out why, but I've been able to reproduce it.
1. Create new empty layer.
2. Select Brush tool.
3. Set brush color (in this case, I chose Red from the Apple palette).
4. Paint two blobs.
5. Select one blob using the Select tool.
6. Switch to the Arrange tool to move the selection. [Aside: It would be great to hold Command to quick switch between tools here.]
7. Move the blob.
8. Press Command-D to deselect.
9. Repeat Steps 5-8 on other blob.
Result: The blobs are no longer red; they're dark orange. Subsequent Deselect (either Command-D or Edit > Deselect) further degrades the color. I also confirmed that it's not just a display issue, because the colors were different when exporting the before/after images as JPEGs.
Are they shifting color space, perhaps?
Curious oddity: I can get this to work when they're on an empty layer above a photo (tried versions with both RAW and JPEG images), but if I start with a completely blank document (i.e., on white), the colors don't shift. Also, the colors in the underlying layer aren't shifting.
I attempted to attach an animated GIF of a video capture, but I'm not sure it went through. If not, here's a link to view an MP4:
https://www.dropbox.com/s/6oprmmtva440m ... t.mp4?dl=0
Is something not working like it should? Let us know.
Thanks for another detailed bug report — it looks like the bug doesn't happen in blank, new images because they use the standard sRGB color profile and this only seems to happen in images that use other profiles. So, when you open a photo, a different profile is used and the bug occurs. In any case, we've been able to reproduce it and we'll do our best to fix it ASAP. Thanks again!