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