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