one more genetics?

Question

A creature is dark brown and has dark brown young. Another of the same creature is green with green young. A man crossed the two to produce heterozygotes. 32 offspring has these colors:
18 dark brown
6 red
6 green
1 yellow

1) How many pairs of genes (not alleles) control color?

2) Write the genotypes for original strains and make a Punnett square for heterozygotes cross. ( an explanation is all I need)

I don't know how to do these complex ones..

Answer 1

DD/Dg=brown
GG/Gg=Green

1)2
2)Dd + Gg
DG Dg dG dg
DG DDGG DDGg DdGG Ddgg
Dg DDGg DDgg DdGg Ddgg
dG DdGg DdGg ddGg ddGg
dg DdGg Ddgg ddGg ddgg

Answer 2

are you sure its one yellow? doesn't add up to 32 then. anyhow if it is 2 yellow then it can be simplified as 9:3:3:1 ratio. i.e. it is again a case of allelic interacation between two genes. i.e. both the genes give their respective colour in respective dominant conditions when the other gene is in recessive state.however the trait is modified when both are present in the dominant state and that gives brown. when both are recessive it gives yellow or rather the lack of pigment.