The patch cables change color when you drag them. The color represents the original color of the necessary Doepfer cable. Doepfer cables are color coded by length (at least in 2014 when I build that patch tool).
Oh, I didn't notice! Nice detail. I'd personally prefer a small note next to the cable displaying the centimeter length of that stretch.

It does however look like doepfer use differnt colors than the colors in sketch a patch; http://www.doepfer.de/a100z_e.htm Also the sketch a patch cables seem to have a maximum length, it cycles through colors until they hit black, then stops.