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