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