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