The best alternatives to Harmony are FarbVélo, Noise App, and Specdrums. If these 3 options don't work for you, we've listed a few more alternatives below.
FarbVélo (Swiss-German for color bicycle) is a playful color picking tool. It follows simple generative rules and lots of random numbers to help you come up with the most pleasing color combinations, or just chill while cycling through color harmonies.
Noise allows you to create personalized acoustic environments for relaxing, meditation and better sleep. Combine different sounds into a pleasant soundscape and store your favorite combinations as mixtapes.