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