If you are saying that the camera output, not the rest of the app, is blue, then you may have gimbal/craft secure connection issue. If you're saying that the whole screen is blank, that's a different story.
On the assumption that it's the first problem, here is what I replied to another poster in a different thread:
I've read about several owners having this issue. Please check the integrity of your gimbal to craft connection. If all the contacts are not making a connection, this is the symptom. Clean the contacts. If that doesn't help, contact DJI support for a method to raise the contacts to bring them together. The camera intermittently working points to connection issue.
If it's the 2nd issue,that's out of my league. Call DJI Support.