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