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