If you want a nice white light then 6000k bulbs should be what your after. In colour temperature terms that should match 'midday' on a bright sunny day in summer.
The factory fit bulbs were 4500k if memory serves correct, and remember that in the time period the headlights were made there were probably not multiple colour temp bulbs available...and factor in Volvo's inherant safety culture of not wanting to dazzle people etc...
I ran bulbs from these people in my S40. Decent quality for the price:
https://www.ebay.co.uk/itm/352287937894
Just make sure you handle them well on installation. Take care as they ignite the gas in the bulb with higher voltage, you should not get a shock if you don't put your finger where its not wanted!