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