Right now, the viewer is only set up to plot Cp. This is closely related to velocity - just in different scale. You could likely modify the viewer to plot velocity instead.
Alternatively, there is an experimental python tool for working with VSPAERO output. It includes a visualization tool. I played with it a while ago, put it on GitHub and made an announcement -- but nobody seems to have shown any interest in it.
https://github.com/ramcdona/OpenVSP/tree/pyVSPAEROThat might be another place you could start playing.
Rob