Historically, lead was very often added to linseed paint to combat mould growth. Whilst it's fair to say that it was a very effective addition, we of course now realise that its use is not desirable for health reasons.
Thankfully, the addition of a mix of zinc oxide and titanium dioxide provide superb levels of mould protection, with none of the health downsides of lead.
You could add this mix into paint, but you will lighten the colour as a result, so it's best to chose paint and colours that already have these compounds added.
The good news.....all of our linseed paint contains pre-mixed zinc oxide and titanium dioxide so you can get the true colour you want with all of the benefits of mould protection.