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