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