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)(28,30)(29,39)(31,33)(32,37)(34,40)(35,38)(1,2)(3,5)(4,6)(7,8)(25,27,31,37)(26,32,33,36)(28,38,40,29)(30,39,34,35)(10,11)(15,17)(16,18)(22,23)(26,33)(27,37)(28,40)(35,39) 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)(26,34)(27,38)(29,37)(30,33)(31,40)(32,35)(36,39)(9,12,14,20)(10,15,11,17)(13,19,21,24)(16,22,18,23)(25,29,31,38)(26,35,33,39)(27,28,37,40)(30,36,34,32)(9,13,14,21)(10,16,11,18)(12,19,20,24)(15,22,17,23)(25,30,31,34)(26,28,33,40)(27,39,37,35)(29,32,38,36)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.