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