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