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