We haven't been able to reproduce this issue. Have you tried re-installing the APK?

~no apps running in the background
~the problem cropped up
~I did not try the video playback on the ipad

~a reboot did not help

I've relayed an inquiry to our device gurus to see if they recognize what may be occurring. Yours is the only report that we've gotten on this issue.

A few more questions..

Do you have any other apps that use the camera on these devices that may be running in the background?

Did you see this effect the first time you ran the Video Playback APK on your Android device, or did it crop up subsequently?

Are you seeing it w/ the Video Playback sample project on you iPad?

Have you tried a full reboot of the affected devices?

Yes I tried making the room darker and lighter and pointing the camera a different spots in the room hoping it would set its own exposure. Nothing helps

to confirm , is this occuring under all lighting conditions - you see it in all context?

I saw the same problem on my galaxy stellar phone running the sample "video playback apk "included on the vuforia site. I would say that it is  something in the vuforia plugin. 

You're seeing that consistently across devices? There's nothing in the SDK that manipulates the white balance in that way. Are you using any other plugins?