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