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