Baseless accusations..

Abdirahman, not interchangeable - yes masc & fem.

The app doesn't show the tips for this lesson, but the android mobile site does (and I'm guessing the other browser-based versions do too).

The tips for this lesson specifically calls out Blue as an example of the color word changing based on gender.

If you prefer doing the lessons in the app, you can still access the tips at your duome.eu page www.duome.eu/YourUsername
Then click the link for whichever of your languages you want to see the words and tips for.

When do we use azraq and when do we use zarqaa2? Are they interchangeable or is zarqaa2 the feminine form?