You are not setting a pitch with the Blue knob but an RPM. Horsepower = Torque x RPM. To Takeoff you need lots of grunt (ie. Horspower and for landing the option of producing the same, but quickly) Therefore you select max RPM for these two events. In addition, having the prop at max. RPM will give you some useful drag on the approach. Try gliding with the engine at idle and then, without increasing throttle, move to Min. RPM and see what happens.
PM