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