The Voges Proskauer reaction usually develops within 20 minutes; note that the red color forms near the surface.  If a brownish color develops (from another reaction of the reagents) this is a negative result.  

The positive methyl-red reaction will be a vivid cherry-red color, developing immediately upon addition of the MR reagent.  Formation of an orange color, indicating only a moderately acidic pH, is a negative result.