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