Shot with the X5S and the 15mm lens. I get a lot of "yellow" from the direct footage and have to colour correct much more than shooting with the P4 P - using the same profile and conditions.  Could this be from the sun setting behind me?  (P4 P does not have this issue!)

This is already colour corrected:

The color range depending on light is different between the two cameras, so the outcome of the footage can be different. The lighting from sunsets can make a difference, do you also use any ND filters? Some of them can have a bit of a color tint on them as well. It would be helpful to see some footage without the color correction to see the extent of it to better determine if there's an issue.

Using 'none' as the color setting, I've observed:

The P4P has a blue bias while the I2 has a very strong earthy tone bias, particularly when the sun is at a low angle in the sky.

In bright sunshine they are about the same

In cloudy weather, the P4P footage tends to have a cooler cast.
If you are a pro - use Raw with the I2.... under challenging conditions