There are lines of different colours on my Xperia's display

1. Find and tap Settings → System → Advanced → Developer options.
2. Drag the slider beside On to the left. 

1. Find and tap Settings → System → Developer options.
2. Drag the slider beside On to the left. 

1. From your Home screen, tap the Application screen icon.
2. Find and tap Settings → Developer options.
3. Drag the slider beside On to the left. 

1. While the device is powered on, press and hold down the power key.
2. In the pop-up menu, touch Power → Power Off until the Reboot to safe mode message appears.
3. Tap OK to restart in Safe mode. 

1. While the device is powered on, press and hold down the power key.
2. In the pop-up menu, touch and hold Power off until the Reboot to safe mode message appears.
3. Tap OK to restart in Safe mode. 

1. While the device is powered on, press and hold down the power key.
2. Touch and hold Power off until the device starts to power off.
3. Wait for the device to restart in Safe mode.

Tip: You can watch this video to learn how to enable and exit Safe mode. 

1. While the phone is on, press and hold down the power key.
2. In the pop-up window, touch and hold Power off until the Reboot to safe mode message appears.
3. Tap OK  and let your device restart in safe mode. 

1. Find and tap Settings → System → Advanced → Reset options → Erase all data (factory reset) → Delete all data.
2. If required, draw your screen unlock pattern or enter your screen unlock password or PIN to continue.
3. Tap Delete all data. 

1. Find and tap Settings → System → Advanced → Reset options → Erase all data (factory reset) → RESET PHONE.
2. If required, draw your screen unlock pattern or enter your screen unlock password or PIN to continue.
3. Tap ERASE EVERYTHING. 

NOTE! To avoid permanent damage to your device, do not interrupt a factory data reset procedure.

1. Back up any important data that is saved on the internal memory of your device to a memory card or other non-internal memory. If you have any encrypted files stored on an SD card, you should also remove the encryption to ensure you can still access them after the reset.
2. Find and tap Settings → System → Reset.
3. Tap Factory data reset → Reset phone.
4. If required, draw your screen unlock pattern or enter your screen unlock password or PIN to continue.
5. To confirm, tap Erase everything.

Tip: You can watch this video to learn how to perform a factory data reset. 

NOTE! To avoid permanent damage to your device, do not interrupt a factory data reset procedure.

1. Back up any important data that is saved on the internal memory of your device to a memory card or other non-internal memory. If you have any encrypted files stored on an SD card, you should also remove the encryption to ensure you can still access them after the reset.
2. From your Home screen, tap the Application screen icon.
3. Find and tap Settings → Backup & reset → Factory data reset.
4. Android 5.0/5.1: If you also want to erase data such as pictures and music, which is saved to your device's internal storage, mark the Erase internal storage checkbox (does not affect the SD card).
5. Tap Reset phone/tablet or Erase everything.
6. If required, draw your screen unlock pattern or enter your screen unlock password or PIN to continue.
7. To confirm, tap Erase everything.

Tips:

• Your device does not revert to an earlier software version of Android when you perform a factory data reset.
• You can watch this video to learn how to perform a factory data reset in Android 7.0