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