Trying to factory reset galaxy, wierd thing happens I got a used T-Mobile Galaxy S Blaze(SGH-T769) from Goodwill. Since it still has information on it, I am attempting to factory reset it. However, whenever I try to boot it into recovery mode, it boots into a strange screen where random bars of color show up. When I boot normally, everything works fine but it has a lockscreen so I can't do anything normally. Besides that, its rather difficult to do anything since the phone is missing its power button.

What could be the reasons for the strange behavior in recovery mode?
Are there any ways to factory reset it besides that?
Should I just give up on the phone?

UPDATE:
I bricked it... Phone won't turn on at all after following guide at https://forum.xda-developers.com/showthread.php?t=1591598, I forgot to uncheck re-partition... even more hopeless?
What button combination are u using and there should be a factory reset in the setting 

Go to settings
Scroll to backup and restore click it
 scroll down and there should be a factory reset button 
I'll probably have to have 30% or more battery  to do so 

I have not had that model of phone but I've had a few Samsung's if  above is not possible u can use Odin mode  and flash new firmware to the device it's very easy to do if u have a PC to do it with 
Look for ur model phone and Odin guide 
Here is one I looked up for u 
Delete the space before and after the word firmware

http:// firmwarefile .com/samsung-sgh-t959