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)(27,34)(28,32)(29,31)(30,37)(33,38)(35,39)(36,40)(1,3,5,8)(2,6,4,7)(25,27,31,28)(26,32,29,34)(30,35,38,36)(33,39,37,40)(10,11)(15,17)(16,18)(22,23)(26,29)(27,28)(33,37)(35,36) involution — undirected(1,2,5,4)(3,6,8,7)(9,11,14,10)(12,17,20,15)(13,18,21,16)(19,23,24,22)(25,28,31,27)(26,32,29,34)(30,36,38,35)(33,39,37,40)(1,4,5,2)(3,7,8,6)(9,12)(10,15)(11,17)(13,19)(14,20)(16,22)(18,23)(21,24)(25,29,31,26)(27,32,28,34)(30,37,38,33)(35,39,36,40)(9,13,14,21)(10,16,11,18)(12,19,20,24)(15,22,17,23)(25,30,31,38)(26,33,29,37)(27,35,28,36)(32,39,34,40)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.