This grasshopper definition is based on 'Reactor' design pattern found in Robert Woodbury's Elements of Parametric Design. A surface is colored based on the proximity of its subdivided parts to a reference point.
This definition is very similar to the previous 2 reactor pattern definitions. Instead of a grid of points, we are using individual patches from a surface which is subdivided. The proximity of each patch to a reactor point is calculated using 'Surface Closest Point' and 'Distance" components. These distances are then remapped to a target domain between 0 and 1. In order to visualize the surface proximities, a 'Gradient' component is used and a default color scheme is selected. The remapped distance values are fed into this gradient component which in turn returns a series of color values that are fed into a 'Custom Preview' component.
The grasshopper definition can be downloaded here.