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