Colored message flags changing to red using IMAP

Setting a colored message flag in Apple Mail for a message in a Zoho account accessed via IMAP appears to work at first. However the flags all appear red when viewed from a different device, and turned red over time on the original device as the client syncs with Zoho. This works correctly with Gmail and other IMAP servers and looks to be an issue with FLAGS . Is this a known limitation with Zoho? Any plans on a fix? It is blocking transferring two domains to Zoho hosting.