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