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