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)(11,22,25,36)(12,21,15,18)(13,17,29,34)(16,26,32,23)(19,27,35,28)(24,37,39,31)(30,38,33,40)(2,7)(3,8)(4,5)(9,11)(10,16)(12,26)(13,24)(14,25)(15,23)(17,33)(18,36)(19,31)(20,32)(21,22)(27,40)(28,38)(29,39)(30,34)(35,37) involution — undirected(1,3,6,2)(4,8,5,7)(10,17)(12,15)(13,28)(16,30)(18,35)(19,21)(20,34)(22,37)(23,26)(24,38)(27,29)(31,36)(32,33)(39,40)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.