If you look closely you'll notice a reaction between the two. Now we have chatted in the past about reactions with copper but we're not using Uroboros' reactive clear or opal here so what gives?
Well, the Peacock Green has a lot of copper.
And the Sunflower Yellow has a lot of sulfur.
When the twixt shall meet they combine to form copper sulfide.
And this reaction as with copper reactions, will intensify depending on heat and length of firings.