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