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)(11,13)(12,20)(14,15)(16,18)(17,22)(19,23)(21,24)(28,35)(32,36)(34,39)(37,40)(1,3,5,8)(2,6,7,4)(10,15)(13,16)(17,20)(21,23)(25,26)(27,29)(28,36)(30,31)(32,35)(33,38)(34,40)(37,39)(1,3)(2,4)(5,8)(6,7)(10,15)(11,18)(17,20)(19,24)(26,31)(27,33)(32,36)(34,39) involution — undirected(1,4)(2,3)(5,6)(7,8)(9,11,14,18)(10,16,15,13)(12,19,22,24)(17,23,20,21)(25,27,30,33)(26,29,31,38)(28,34,35,39)(32,37,36,40)(9,12)(10,17)(11,19)(13,21)(14,22)(15,20)(16,23)(18,24)(25,28,30,35)(26,32,31,36)(27,34,33,39)(29,37,38,40)(9,13,14,16)(10,18,15,11)(12,21,22,23)(17,24,20,19)(25,29)(26,33)(27,31)(28,37)(30,38)(32,39)(34,36)(35,40)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.