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