Bricks, Masonry, Asphalt and Concrete - Plastic joints in concrete - removing them

I have a concrete walkway into which ugly white plastic strips were embedded at the joints, apparently when the walk was poured. These seem to have a plastic upper section and an aluminum lower part going about an inch and a half down into the slab. I don't know who thought plastic would last as long as concrete, but after 15 years the plastic has yellowed and split and looks like hell altho the concrete is in good shape. I'd like to paint the concrete but suspect the plastic will flash the paint or at least will chip in short order. I'd like to remove the plastic things. Is there a method for removing this stuff?

The plastic joints need to simply be removed at the tops and replaced with
SL2 which is a rubber like material that is poured into the joint and expands
and contracts when dry. This should be done by the concrete contractor as it's messy if done wrong. It's arguably the best material for expansion joints and looks much better than wood. It is used in Disneyland in all the concrete
work.

Thanks for your advice! A few questions:
First, some of the walks don't have the plastic joints, just grooves like a sidewalk. Is it necessary to replace the plastic?
Second, whoever removes it is going to have to split and yank vertically - it seems to be stuck. What's the easy way?
Third, what color is SL2 and can it be painted?

Only the top of the plastic material is cut out with a knife. Then the SL2 is poured in
via the tube. It is colored a gun metal grey (I guess to match concrete). I don't think it's paintable. Yes, the SL2 needs to be applied in that application because there's no material cushioning the expansion/contracting now. You should have a concrete contractor look at this. It should not take long to
take care of this.

Well, I've tried 3 concrete contractors and none of them is interested in even looking at them, so I guess I'll need to do it myself. My first question would be if they are necessary (why not just leave the open joint?). As I said in my first posting the walkway has plenty of joints but only a few that have these plastic things. Why are they needed? I could send a photo.

I found SL-2 on the internet and it can be tinted. None of the contractors had heard of it.