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