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