There are several possible reasons why your iPad 6 is showing colored lines and freezing. Here are some troubleshooting steps you can try:
Restart your iPad: Press and hold the power button until the "slide to power off" option appears. Slide the button to power off your iPad and wait for a few seconds. Then press and hold the power button again until the Apple logo appears.
Check for updates: Go to Settings > General > Software Update and check if there are any available updates for your iPad. If there is an update, download and install it.
Reset your iPad: Go to Settings > General > Reset > Reset All Settings. This will reset all your settings to their default values, but it will not delete any of your data or apps.
Restore your iPad: If none of the above steps work, you can try restoring your iPad to its factory settings. Before you do this, make sure to back up your data. You can do this by connecting your iPad to a computer and using iTunes to create a backup. Once you have a backup, go to Settings > General > Reset > Erase All Content and Settings. This will erase all your data and settings, so make sure to have a backup.
If none of these steps work, it may be a hardware issue. In that case, you should contact Apple Support or take your iPad to an authorized repair center.