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