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