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