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