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