Do you have a fancy custom loading animation instead of an UIActivityIndicatorView? You may want to check if it has an accessibility label so a VoiceOver user knows that something is happening. Something like "In progress" or "Loading" could work.
You may also find interesting...
Do you know when a UI element is greyed out to show that it is disabled? Yes, there is an accessibility trait for that too: .notEnabled. VoiceOver will say “dimmed” after its accessibility label and Voice Control and Switch Control will skip it.
Custom actions work as great on Switch Control as they do in VoiceOver. It makes navigation much, much, faster and you’ll be able to find all those custom actions in the Switch Control menu.
You should convey important information in multiple modes, not just color. If you are still required to do so, at the very least you should complement that info with other modes, like symbols, if the user requested differentiation without color.
