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