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