I agree that the question is unclear. I personally don't know the example of the labrador and would need a reference (or a description from you) to talk about this specific case study.
The following tables are displaying all possible kind of interactions (in a haploid and in a diploid) of two bi-allelic loci. Hope that helps! source (wiki)
**For Haploids (the concept of dominant epistasis does not apply)**
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**For Diploids**
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