I've found the larger auto supply wholesale+retail stores often have a better selection of wheel paint than the smaller retail-only auto stores. If you can find one that services the custom car market they often have even better selections. Although Duplicolor is a common touch-up paint brand and they do make special wheel paints, the color selection for wheels is very limited. I've often found better selections of wheel paint in other brands. Cap color only puts you in the ballpark. I've often bought one as a test paint and ended up using it as an undercoat with a better matched top coat. You can even use undercoats to your advantage to slightly darken or slightly lighten the top coat as long as the top coat is applied evenly and not too thick.

As another option, here's a link to the Volvo paint code numbers, descriptive names and models they were used.
https://www.volvoclub.org.uk/paint_colour_codes.shtml

At the very end of the list are the standard wheel paint codes. For the standard square slotted wheels used in many models I believe it was #930 "Silver". Note a few lines up that #930 was also available as a body color on 850 models called "Silver Metallic". Volvo sells touch up paints in small spray cans in addition to the touch-up bottles. You'll have to check on availability through your dealer, but almost certainly it's going to be a long order wait and you're going to need a number of cans so won't be cheap.

A much better option if you want an exact match are autobody shop paint suppliers. They should be able to lookup that Volvo paint code. Looking up #930 as an 850 body color may be simpler than looking it up as a wheel color. If they can't find the formula for their pigment mixer then they should be able to do a computer color match. For your small application they can make up tall spray bombs. I did this some years ago when I was doing rusty 140 quarter panels and rockers. It worked well. For the outsides of 4 wheels you'll probably need a bit more than one large can, so get two for sure. Quantity one was a bit expensive, but additional cans are almost as cheap as store bought. The paint shop can advise what type of paint they can mix up that would be best for wheels, typically was an acrylic enamel, but there may be new and better formulations.

I've painted wheels before. It's extra tricky to do a good paint job on wheels, especially with a spray bomb. Trying to get an overall glaze is especially tricky without getting runs or orange peel. It's perhaps better to settle for thinner coats and a satin finish. After the initial cure, a polishing compound (finer than rubbing compound) may be needed to get an even surface look.

Wheels are subject to harsh conditions and abrasion, so after the initial cure I always do a final bake for maximum hardness. You can use heat lamps, preferably at least two, doing one wheel at a time, turning them during the day, even an overnight bake. Do not use a kitchen oven, it will stink up the house for days (someone I know did that, not me). I once did a set of wheels on a warm day. I baked the whole lot in my greenhouse on the bench in full sun. Those wheels stayed too hot to touch for most of the day. It turned out really well and the paint stood up during tire installation and since then.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now