We've been made aware of this display issue on Chromebooks. It's a challenging problem to solve as it only happens on Chrome but not on Android, so the fix needs to not cause new issues for our Android users!
If you continue to have issues, here are two workarounds you can try:
1. Go to Settings > Device > Display and enable Night Light
Try this first as the optimal workaround, as it can make the problem go away in Sketchbook without strongly affecting the rest of your device experience. However, we have found that it doesn't work on every Chrome OS device.
2. Adjust your Display Size - try adjusting the resolution in the 10% increments of the slider
We've found that adjusting the display size is always successful in making the problem go away, though there's no specific resolution that magically works - it differs from device to device. And this may not be a workaround that is ideal for how you want to work on your device.
If you have further questions or issues, please reach out to us at firstname.lastname@example.org.