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