Varnish or paint pine wood chairs or something else?

Nothing is worse than having five different wood tones in the room. Better to just choose a solid different color. So acrylic paint and then just a color you like.

Well... I can think of worse things. You just have to decide for yourself whether you can live with it or not. We also currently have several wood tones in the living room. It doesn’t bother me because the sets are somewhat passive. Gradually they will be replaced.

Yeah, well, a 90s wall unit in Wenge with lots of glass is worse or a high-gloss faux leather bed with UV lighting. But I didn't want to mention that explicitly. Which is where you’ve got me now—I have to call my therapist first.

I like it this way, with the different wood tones. It shows me that people live there and that some things change so much that they simply "no longer fit." I find that very nice and would either just leave everything as it is or paint the chairs in different colors.

I now have an oak floor and an oak table and I don't really like that they match so well. Wood always looks good, though. :)

However: pine is still pine. And even if the shade matches, it is still a different wood, which will always be visible.

Thanks to you all. That is already helpful. Regarding the oak tone, I understand that this will not be an oak chair. We first considered oak chairs, but we keep coming back to this "cheap" chair because we are very satisfied with the seating comfort and it can also be easily repurchased.
Otherwise we would have taken white, but the contrast is too harsh for us.

I think white and black as well as every shade in between goes with everything. If the extremes are too extreme, you take something in between (commonly called gray). If you like wood grains and don't mind that it is not exactly like the other wood surfaces, then you can glaze and (clear) lacquer or oil. If not, then simply paint opaque.

can you glaze and (clear) varnish

Both or either? Then the varnish glaze would be an option for me.