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