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