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