If shopping and want to look for info on items like this, there is a great source here:
You can pick out a specific year, make, model, etc and look at any of the parts on that model, even down to what pipe goes where!
This is the 2020 model 25 B and the sink line goes to the grey, not black tank.
The bath vanity sink does go to black.
Click this pic for better view but the black is orange and the grey tank is blue in this drawing.
Hint? Black is the one the stool fits on!