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