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