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