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