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