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