It is because of system tolerances. The yellow areas (in your case thin lines) indicate that the draft is smaller than selected in the dialog. You have specified 3° draft in the Boss-Extrude, and also 3° in the property manager.
The actual draft fluctuates a little bit around the 3° creating the yellow lines. If you change the value to f.ex. 2,99° they disappear.
It is because of system tolerances. The yellow areas (in your case thin lines) indicate that the draft is smaller than selected in the dialog. You have specified 3° draft in the Boss-Extrude, and also 3° in the property manager.
The actual draft fluctuates a little bit around the 3° creating the yellow lines. If you change the value to f.ex. 2,99° they disappear.