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