Some editing programs allow the editor to show two or three screens at a time. This is so the editor can see past or future clips and color and contrast balance accordingly.
In MovieStudio, any effects updates are added in real time. However, you can turn the effect(s) off to see before and after by unchecking them on the FX panel.
Steve's right -- Vegas Pro has a split screen option, but Movie Studio does not.
In Vegas Pro, you can copy a frame or an image to the clipboard, then enable a split screen view on the main screen to compare the reference image to the frame at your playback cursor.
Probably the easiest way to do it in Movie Studio is save your reference image as a snapshot (PNG file), then open that reference image in the Trimmer display, while comparing and color correcting in the main display.
A little more hassle, but probably worth it, would be to temporarily add another track at the top of your project, put your reference image on that track, and apply a cookie cutter or pan-crop to it so it only occupies part of the screen, letting your playback frame show through for comparison. You can toggle the entire track on and off when you don't want to see the reference shot. You could stretch the reference event out really long on the timeline so it is available throughout your whole project.