The Colossal's vertical element is 21.5 feet, this is not including the base tube and insulator height.These two antennas are basically the same 5/8 wavelength as far as RF is concerned. The reason the V-5000 and V-58 tune physically shorter is due to the capacitive loading that takes place at the base where the bottom tubing sections overlap with the insulator in between.
I'll bet the colossal 5/8 wave tunes up with very similar measurements due to its gamma type capacitor placed in the same location. We don't hear comments about this because the length is not published, it looks good and "it costs too much for it not to be good".
The spec's are right on their website