Lovely view, but can't see the pine walls and trims.

I stained the beams pecan to match the hardwood floors and the kitchen cabinets, the pine is darkening due to ample sunlight.

Pine has plenty of tannins. These tannins give it colour. When pine is painted, it has a tendency to leach these tannins into the paint. This means that white paint will slowly (or quickly) turn yellow/orange because of the "stain" the tanins add to the paint.

To prevent this, you can add a "tannin blocker". This is a specialty product that is ordered through a professional company. It is not cheap. It should do the job. You would need to strip the stain off the pine (yep...back up the ladder) and then apply the tannin blocker and then paint (waiting the appropriate amount of time between blocker and paint...of course).

There is no stain or varnish on the pine now, it's just plain pine, so I guess I can skip that step. Just tannin blocker, then paint? My question would be what kind of paint for that milky finish, some people recommend watery white latex paint, then apply a varathine finish, while others recommend an white oil based stain. Any recommendations?