The change of colors is a part of the design only. 134 mm from the sketch you’ve sent is the distance from the bottom of the receiver to the GNSS antenna’s physical location inside it.
If you enter the base position manually, you will need to calculate the GNSS antenna’s physical location. To do it, add the pole’s height and 134 mm to the known base position on the ground.
When you average the base position, you get the distance to the antenna phase center right away. You don’t need to add any offsets for that.
The CSV file contains the coordinates the rover received from a base station. So, it should be the same coordinates that you enter on the base station unit.
In AUSPos and other PPP services, you will need to enter the pole’s height in the Height field and choose the EML_REACH_RS2 Antenna Type.
You can apply the antenna phase center value in RTKLib. To do it, you will need to upload the atx file. You can do it as follows:
Download the igs14.atx file from here
Go to RTKPost Options -> Files
Add the igs14.atx file to both Satellite/Receiver Antenna PCV File ANTEX/NGS PCV fields as shown:
Go to the Positions tab
Enable the Antenna Type option and choose the EML_REACH_RS2 antenna from the list