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