Shells are either white or blue.
There are two genes for shell color and I believe they are dominant,
so if just one passes the shells of female offspring will be blue.
If your Araucana is pure, he should have two blue shell genes,
and no brown coating genes.
The brown coating is a whole other string of genes, at least a dozen.
That's about all I know....and it may or may not be correct.
Go ahead and hatch some from that pair,
make sure no other cock/erels are present for at least 3 weeks.
Probably have at least a 50-50 chance of an olive egger from the pullets produced.