light_vertices.py

import bpy
import math
import mathutils

def magnitude(v):
    return math.sqrt(v.x ** 2 + v.y ** 2 + v.z ** 2)


COLOR = mathutils.Color((1, 1, 1))
RADIUS = 10

obj = bpy.context.active_object
center = bpy.context.scene.cursor_location
vcolors = obj.data.vertex_colors.active.data

for poly in obj.data.polygons:
    colors = []
    for idx in poly.vertices:
        vert = obj.data.vertices[idx].co
        delta = vert - center
        distance = magnitude(delta)
        atten = 1 - min(distance / RADIUS, 1)
        color = COLOR.copy()
        color.v *= atten
        colors.append(color)
    for idx, ptr in enumerate(poly.loop_indices):
        color = colors[idx]
        vcolor = vcolors[ptr].color.copy()
        vcolor.r *= color.r
        vcolor.g *= color.g
        vcolor.b *= color.b
        vcolors[ptr].color = vcolor