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