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)(26,29)(31,33)(32,37)(38,39) involution — undirected(1,2)(3,7)(4,5)(6,8)(9,11,15,16)(10,13,12,18)(14,22,23,19)(17,24,20,21)(26,29)(28,36)(31,33)(34,40)(2,5)(6,7)(10,12)(13,18)(17,20)(21,24)(25,26,30,29)(27,33,35,31)(28,37,36,32)(34,38,40,39)(1,2)(3,6)(4,5)(7,8)(9,12,15,10)(11,18,16,13)(14,20,23,17)(19,24,22,21)(25,27,30,35)(26,31,29,33)(28,34,36,40)(32,38,37,39)(1,2)(3,6)(4,5)(7,8)(9,13,15,18)(10,16,12,11)(14,21,23,24)(17,22,20,19)(25,28,30,36)(26,32,29,37)(27,34,35,40)(31,38,33,39)(1,3,4,8)(2,6,5,7)(9,14,15,23)(10,17,12,20)(11,19,16,22)(13,21,18,24)(25,29,30,26)(27,33,35,31)(28,37,36,32)(34,39,40,38)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.