One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,8)(4,6)(5,7)(9,10)(11,21)(12,26)(13,19)(14,17)(15,20)(16,23)(18,29)(22,31)(24,32)(25,30)(27,33)(28,34)(35,38)(36,40)(37,39) involution — undirected(1,3,5,4)(2,6,7,8)(9,11)(10,16,20,32)(12,22)(13,23)(14,24)(15,25)(17,21,19,30)(18,31,34,40)(26,39,33,35)(27,36)(28,37)(29,38)(10,17,20,19)(12,27)(16,30,32,21)(18,26,34,33)(22,36)(28,29)(31,35,40,39)(37,38)(1,4,5,3)(2,6,7,8)(9,12,13,28,15,27,14,29)(10,18,17,33,20,34,19,26)(11,22,23,37,25,36,24,38)(16,31,21,35,32,40,30,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.