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