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