I think this has been suggested previously, but I'm gonna suggest again so it's a higher chance of being seen. The background of the new volume slider matches too closely to the volume level so under certain conditions, it's difficult to tell what the volume on your phone is without playing something. This can be fixed by either increasing the contrast between the volume level and background, or by making them different colors like in previous versions. If the volume level was blue with a gray background, it would be perfect, or a darker background with the same volume color.
I know this was a long winded post, but it's an easy change that would make the user experience so much better.
Thank you very much for your suggestion. Your suggestion has been communicated to the developer and the development project manager is reviewing the content. After reviewing your suggestions, we will apply them to the official version if your proposal matches our concept. We appreciate your contribution to the beta program.
