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