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