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