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