This PowerScript uses Illustrators colorbooks to calculates the closest Pantone or Spot color to a process color.
Unlike Illustrators built in Recolor Artwork tool, you can easily just select a single color in your document then see a list of multiple spot colors and choose what you think is the best match.
When a Pantone color is converted to a process color if often looses some saturation, so the closest match to the process color may not be the right one. Based on your experience, you can pick a color which is technically not as close to the process color but is much more likely to be the original Pantone color.
This script calculates the difference between an RGB or CMYK color and the colors in the colorbook. This is given a DeltaE number, the lower the DeltaE number the closer the match to the spot color.