After home button replacement my screen colour went negative I just replaced my home button. But when I reassembled it, the colour went negative. From red to blue and blue to red. Although I've turned on and off the invert colour function, it's still not displaying right. Did the screen break? Or do I just need to double check the cable?

The screen also looks like it's flashing really fast which normally it doesn't.
That definitely looks like a hardware problem as the invert colours feature doesn't really look like that. The flickering also reinforces this as this would not happen normally. I would reopen the device and make sure that all connections are connected properly and intact.