What type windows are you looking to go with? Will they have a wood interior?

I would restain the lighter wood, to match the darker, so they are all alike. Looks like you have several color stain there. You cant lighten the dark, but, you can darken the light. Sand well first. Are you sure that isnt paint on the darker color, rather than stain? If so, then put the same on the lighter stuff, or decide to paint all the trim and windows in your house so they all match.

Yes, the inside will be wood made by Pella. We can choose a mahogany stain and would probably be fine, but it wouldn't match the other windows in the home. This room is away from the others.

I'm not sure if the color is a stain or paint, but probably paint. It would be a tedious job to sand and repaint as we have 23 windows that have the same stain as the small window in the picture, and all the baseboard and door facings are the same.

They will have a wood interior and we do need to stay with Pella. The size window opening we need is the size they offer. Other window companies doesn't have windows large enough to fit our opening. We checked with a few already.

Most all companies make the same sizes or very comparable sizes. Pella does not make a size that is not made by a higher quality company or that is exclusive to Pella.

The door shown is not a wood door but is painted , and the dark brown trim is paint or really think gel stain. I would paint them all white and move on since I like white trim but couldn’t you match that finish on the new windows?