Wearable devices that exchange data with each other?

I am trying to build a wearable device that has an RGB LED, whose color is controlled by a knob. When two devices are close to each other, their LED colors will be set to the color in between of the two original colors.

For example, if one person sets the LED on her device to red, and another person sets his to blue, both of their LEDs will be changed to purple when they stand close to each other (about 15" distance between the two devices).

Is it feasible and what tools / parts should I use?