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