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