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