My text is black in the blue bubble on imessage - I did not invert colors. The screen is regular otherwise

It would be better if you can please re-post with a screenshot, in order to understand the phenomenon better. Images / pictures speak louder than words. (Do not provide any personal credentials, such as email id, apple id, IMEI number, Serial Number, Phone number, Order ID, if you are sharing a map ensure your location is not identifiable. etc)