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