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