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