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