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