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