Which is water shut off valve here?
This appears to be the plumbing for your water heater - as such, while there are shutoff valves for the cold into the heater and the hot out of the heater, the cold running to your various fixtures (and to here - the main water shutoff) is almost certainly somewhere else.

The water shutoff valves here are the red and blue metal handles that are shaped somewhat like:

-\_/-


Turn them 90 dgrees so the handles are out of line with the pipes they are on, not in line with them to shut off - reverse to turn on. 

Check your water heater manual to see if you need to shut it down before turning the water off. That's pretty common.

The other red and blue handles near them appear to be for some sort of flushing procedure with the capped ports near them.