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)(13,27)(14,17)(15,22)(16,25)(18,28)(20,29)(21,31)(23,30)(26,38)(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)(19,27)(22,28)(24,37)(25,34)(26,36)(32,40)(33,38)(35,39) involution — undirected(2,4)(9,12,13,25,14,26,28,39)(10,16,18,24,17,32,27,38)(11,20,21,34,23,36,22,35)(15,29,30,37,31,40,19,33)(10,17)(11,21,23,22)(15,19,31,30)(16,32)(18,27)(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.