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