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