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