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