Texture quailty is terrible only in iOS

In Android, my UI textures are just fine (ASTC).

Look at the comparison here: https://i.hizliresim.com/lqbL6J.jpg

But, as you may see, in iOS, colors are wrong and texture quality is terrible. Quality is good if I set compression quality to ‘Highest’ but colors are still wrong. How can I achieve high quality images?

Edit: Only setting pvrtc compression quality to 4 from project settings also fixed quality problem without increasing images size. But colors are still wrong.