The valve may be installed upside down; therefore the mixer cap assembly is mixing water "backwards."
While observing the cap assembly, find the red/black collar and tab. This red tab needs to be touching the stationary black tab on the cap and in the up position, pointed upwards towards 12:00. In the picture below, the red tab is facing downward, and in the 5:00 position, which is incorrect.
To correct the issue of the hot water coming on first, refer to the following steps below:
1
Turn off the water supply to the valve.
2
Remove the screws on the left and right side of the black cap.
3
Remove the metal collar.
4
Pull out and rotate the cap until the stationary tab and collar are in the upward position.
5
Reassemble and turn on the water.