Why are the pictures taken by Canon 600D blue?

The problem of white balance setting, generally speaking, the default of the machine should be automatic white balance.

However, when the flashlight is used indoors, the white balance will deviate. If the landlord is a novice and doesn't know much about the internal settings, you can consider using a processing software to adjust the white balance later.

Of course, if you can find the white balance setting in the machine, you can adjust the white balance by adjusting the color temperature value.

If the picture is blue, then you should increase the color temperature. As for how high it is, it depends on your own experiment. Take more pictures and find a suitable value.

I hope it helps you.