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