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