Open CV upgrade

I have an Android app that detects colors and displays text depending on the color. The app has 2 parts a live camera view and an image import. all images are detected in image import, but only white, black and grey are detected in live view and I need this fixed. I also need to use the flash, like it's used in the camera, in live view on touch screen to detect the right colors at night. I also need to make it available for the earliest possible Android sdk and the latest, cause right now I have from api 21 to 27, so it's the latest but I don't know if I can use an earlier api. The project is made to be used in AS 2.3.