Making Marls Project

Hi marl experimenters,
I’ve been working with Cecelia Campochiaro’s amazing “Making Marls” text, working specifically on the Fabian project, p. 218. I’ve used the three suggested shades of Shibui Pebble. Problem: starting the second, lightest stripe, the medium blue and light-shaded marl looks just like the first stripe, which is a mix of darkest blue and light yarns. I ripped that out, and tried doubling up on the lightest shade–no go. It wasn’t marled and looked flat compared to the marled section beside it. I’ve ordered a very light shade of Pebble, Ash, to see if mixing that with the light blue will work.
Thoughts? Anyone else experience this issue?
Maria Fisher