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)(27,32)(28,38)(29,33)(30,34)(31,36)(35,39)(37,40) involution — undirected(1,2)(3,7)(4,6)(5,8)(9,11,14,20)(10,15,17,18)(12,19,13,21)(16,23,22,24)(25,27)(26,32)(28,36)(29,30)(31,38)(33,34)(35,40)(37,39)(1,3)(2,5)(4,8)(6,7)(9,12,14,13)(10,16,17,22)(11,19,20,21)(15,23,18,24)(25,28,39,40,31,32,30,33)(26,29,34,27,36,37,35,38)(2,6)(3,8)(11,20)(15,18)(19,21)(23,24)(25,29,31,37)(26,33,36,40)(27,30,38,39)(28,35,32,34)(2,6)(5,7)(9,13,14,12)(10,16,17,22)(11,21,20,19)(15,23,18,24)(25,30,31,39)(26,34,36,35)(27,37,38,29)(28,33,32,40)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.