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