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