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