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