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