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