During exercises there are sound effects to notify you when a move/pose is done. I sometimes even play while not looking at the screen without issue. Before starting, the ring and leg band need to be at a specific orientation. For example, when you do an overhead press, the ring needs to be horizontal. Tipp (the figure that shows you the moves) is visible including the text how you should be standing, and you have enough time to come closer to the screen to read this.
I cannot really say if the contrast is high enough. There are a lot of bright colors, also showing how much repetitions are left. Showing how moves are done is shown by Tipp with a white background, as shown in the screenshot below (this is actually before starting an exercise).
There are also parts in the game where you jog through a forest, grassland or something else. There you can do various things to obtain more coins, take shortcuts or evade enemies. Those moments cannot be paused or slowed down unfortunately. Maybe if you look at a gameplay video you might see if the contrast is high enough. Doing these things are not necessary though, you can still progress the game.