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