Have you ever played with a chicken calculator? It's fun for the novice, and I'd imagine a tool for the more experienced.
Toss a pic of the birds in question up when you get a chance.
https://kippenjungle.nl/kruising.html?mgt=E:e^b/e^b,Pg
g/Pg,Ml:Ml/Ml,Mh:Mh/Mh,I:I/i+&fgt=E:e^b/e^b,Pg
g/Pg,Co:Co/Co,Ml:Ml/Ml
If you click the "show examples" button, you can choose a general color pattern w/o knowing the actual genotype. It's not that accurate that way, especially using a 3 way cross, but it can give you a general idea.
For example, this is for a Jubilee Eng Orp rooster, and a Light Brahma idea I'm toying with.
If you want more of an input selection, click on the link the red arrow is pointing at. It opens a new page, scroll all the way to the top, and you'll see some drop down windows, 4 tiers and 2 stacks. The second tier from the top is English language. Select the two color patterns you would like to play with, and click "to chicken calculator."
What I'm describing is not the most accurate, but without knowing the exact build of the Cochin mix, I don't think there really is an accurate ay without breeding and testing to see what you get.