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