Why my iphone 6 plus goes into Red Screen?

I don't know. We need details.

If it won't respond to anything, hold down the home and power button until you see the Apple Logo appear.

Try the simple thing first. Reset your iPhone. Press and hold both the Home button and the Sleep/Wake button continuously until the Apple logo appears. Then release the button and let the device restart. You will not lose data doing this. It's like a computer reboot.

If that doesn't help you most likely have a hardware failure related to the screen. Make an appointment at an Apple Store to have your device examined by a technician. Or contact Apple Support.