region(r1)
region(r2)
region(r3)
region(r4)
region(r5)
region(r6)

hue(red)
hue(green)
hue(blue)
hue(purple)

next(r1,r2)
next(r1,r3)
next(r1,r5)
next(r1,r6)
next(r2,r3)
next(r2,r4)
next(r2,r5)
next(r2,r6)
next(r3,r4)
next(r3,r6)
next(r5,r6)