One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(5,6,8,7)(9,10)(11,19)(12,16)(13,26)(14,17)(15,22)(18,29)(20,35)(21,37)(23,40)(24,36)(25,33)(27,30)(28,34)(31,39)(32,38)(9,11,14,20)(10,15,17,30)(12,23,25,39)(13,27,29,22)(16,32,33,37)(18,35,26,19)(21,28,38,24)(31,36,40,34)(2,4)(11,20)(15,30)(19,35)(21,38)(22,27)(23,39)(31,40)(32,37) involution — undirected(9,12,14,25)(10,16,17,33)(11,21,20,38)(13,28,29,24)(15,31,30,40)(18,36,26,34)(19,37,35,32)(22,39,27,23)(5,7,8,6)(10,17)(11,20)(16,33)(18,26)(21,38)(22,27)(23,39)(34,36)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.