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