Myrostersucks,
The min clean speed is always V ref 40+70 for the NG, as long as you fly above the amber arc. Below FL 200 this is displayed, while above that it requires a trip to the approach ref page of the FMC. As per the FCTM, fly at least 10 kts above the amber arc when in hdg sel. The figure of Vref 40+100 above FL 250 is only for holding when more accurate speeds are not available from the FMC/QRH.
Cheers