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