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