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