Based on my experiences, I don't mix stains to any wood finishes. I apply first the stain direct to the wood and apply the finish up to topcoat. I prefer tung oil than using linseed oil. Tung Oil blends and darkens the wood when applied.
If you really want to ad color to linseed oil, then the stain or tinting color must be oil based. But you should stir the mixture frequently to avoid uneven color during application.
If you really want to ad color to linseed oil, then the stain or tinting color must be oil based. But you should stir the mixture frequently to avoid uneven color during application.