1993 XM Turbo CT owner in Tampa, Florida

[Dieselman]

Firstly, you did well changing that sphere, it's often neglected. You should have been able to reach it with the exhaust still on, just push the heat shield over the top of the silencer, you will see it has a notch to go round the spare wheel carrier support. It's best to remove the spare wheel carrier to create space to work.

Those spheres are often tight but shouldn't be if the system is fully depressurised in the correct order. Engine running, lower car, loosen 12mm bleed bolt, switch off engine. Any residual hydraulic pressure will lock the threads.
Giving the sphere a few taps with a heavy hammer, either before, or while attempting to loosen, often frees any stuck ones.
Did you lose much fluid when it came undone, or just a small amount? Excess loss indicates there was some residual hydraulic pressure, or a ruptured sphere.

Interesting feedback regarding ride quality, Citroen spheres are the best as they have tight control over the dampers fitted. The two Hydractive spheres don't have any dampers, so it shouldn't be relevant for this sphere.
Ride quality is a result of sphere volume and gas pressure and the damper fitted.
It's possible your car had Comfort Spheres fitted, check the P/no's, pressure stampings on the spheres and measure the damper centre hole diameters.
Xm were designed to ride more stiffly than previous Citroens, so some people did fit comfort spheres, at the expense of ultimate handling.

The colour is irrelevant, Citroen just changed from green to grey universally.

Citroen spheres come in two flavours, standard, or multicouche.
Standard have a single membrane, multicouche have a laminate of three membranes, 2 urepan and a centre PVC layer. PVC is impermeable to gas so these spheres last a lot longer, but are very expensive and not available for all fitment locations.
Multicouche spheres have three dot type impressions, 120 degrees apart, stamped into the steel round the filling plug and technically can't be refilled as the PVC layer is probably already breached due to flexing, so they then rapidly fail.
I do have one, or two and do refill them well before they are depleted, so no rapid failure, yet.
Multicouche spheres were developed for anti-sink cars with hot engine bays, as those features cause greater gas permeation.

Have your old spheres pressure tested and re-gassed if possible. If they are below 10 Bar you are chancing the membrane rupturing, but your description of the ride quality being good indicates they all have good pressure.

Your car is in fantastic condition underneath, I think every member in the UK is very envious.

Thank goodness for emoticons, we might have had to prove we were over 18.

[xantia_v6]

At some point in the early 2000s Citroen started painting all genuine replacement spheres grey, regardless of what model car they fitted, or what internal construction. I heard that it was because of a European norm about colour codes for pressure vessels.

Most after- market suppliers continue to paint them green.

The increased harshness of ride could be because the replacement spheres are a different specification (did you check the markings on the old spheres?). I is also possible that you have some air in the suspension lines which will cause rather rough suspension.

[Dieselman]

Further to previous comments, your car being Rp5882 means it is a late Hydractive 1, but being classed as a 1993 car may have had Hydractive 2 spheres fitted at some stage previously.
H1 uses 400cc spheres both front corners and 500cc in the centre (total 1300cc), whereas H2 uses 450cc spheres in all front positions (total 1350cc). Additionally H2 centre sphere is at higher pressure so the complete volume of pressurised gas is even greater. H1 has 75 Bar-Litres, H2 has 78.75 bar-Litres, across the front axle. That equates to a 5% softer spring rate.
The damping of the corner spheres is also slightly more relaxed on H2 cars, so it will feel generally more compliant in either soft, or firm mode.

All sphere information is contained in the Citroen Private Car technical handbooks in the link. viewtopic.php?f=13&t=11023
We don't have all years, but the information does cover all suspension sphere changes. You will see H1 spheres have smaller damper orifices, as well as different volumes and pressures.
You can drill the centre orifice to give a more relaxed ride for low frequency undulations. The spring disks are for high frequency, sharp shocks.

I have some IFHS spheres and some genuine Citroen ones and can't feel any discernible difference. I have previously noticed stiffer damping with other brands of spheres, which couldn't be made to ride correctly, irrespective of gas pressure, or drilling the centre damper orifice out a little.

In your image you can see the height corrector linkage and bearing are dry of lubrication. Apply grease to the bushing the spring rod passes through and the ball joints on the dog-bone linkage to ensure smooth operation and longevity.
Also grease the height selector "flag" and the bushing that rod runs through.

If it's supposed to move, or you want it to in the future...grease it.