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