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