I have created a web map that includes publicly available Sentinel-2 infrared satellite imagery. In my web map the imagery displays as expected, though when I open it in field maps on both my iPhone and iPad, the infrared imagery is black and white. I'm yet to work out the reason why this is happening - any advice would be appreciated!
Sentinel 2 views use a template to display correctly in arcgis. My guess is that the field map app lacks the capability to recognize and display an image service layer the way it does in arcgis Pro or web maps. Try downloading and using the actual source imagery using the bands you want.