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