Hi @MADssense, and welcome to the forum!
You’re right, phases aren’t displaying with their associated colors on the gantt overlay due to a bug you’ve discovered. Instead, the lines are black which makes it extra hard to read in dark theme. If you switch to the light theme, you’ll be able to see the phases better, but they will still be black until the bug is fixed up.
We’ll let you know as soon as this bug has been fixed up.