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)(27,34)(28,29)(30,33)(31,40)(32,36)(35,37)(38,39) 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)(25,27,30,36)(26,32,33,34)(28,39,40,35)(29,37,31,38)(2,6)(3,7)(25,28,29,26,30,40,31,33)(27,35,37,34,36,39,38,32)(9,12,14,13)(10,16,17,21)(11,19,20,22)(15,23,18,24)(26,33)(27,36)(28,40)(37,38)(3,7)(5,8)(9,13,14,12)(10,16,17,21)(11,19,20,22)(15,24,18,23)(25,29,30,31)(26,28,33,40)(27,37,36,38)(32,39,34,35)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.