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