Hmm his parents were more than likely blue based.
Blue is recessive so it requires copies from both parents to appear visually. Although it is possible for two green series birds to produce a blue series if both are split blue.
At least one of them had to have a violet gene and one had to have a dark factor for him to be violet cobalt. Both violet and dark factors are dominant genes, so they cannot be hidden in split form.
As for his recessive pied: Either both were recessive pied. One was recessive pied, the other split. Or both were split for recessive pied as it requires two copies (one from mom and one from dad) to show visually on the chicks.
I'd have to see more pictures of his wings to figure out if he's opaline or not. BUT IF HE IS! His mother was opaline and his father was either split for it or opaline himself.
Opaline is sex-linked so it only requires one copy (from dad) to show visually in females and requires two copies (from mom and dad) to show visually in males. It cannot be hidden in split form on females but it can be hidden in males.
Otherwise it's hard to say what his parents actually looked like, there's a lot of factors that play in. You can only guess.