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