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