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