The silver rims are likely to have been sealed with something to keep the finish, so they will need a good etch to bring back to bare metal.
If possible get them put through in the same batch at all stages, etch, anodise, colour and seal. This will give the best chance of matching colour and finish quality.
Hold them on the inside of the tyre seat i.e. where it will be hidden by the rim tape, then fixture shadows will be hidden.
Coloured anodising is a cosmetic ‘soft’ finish and is more likely to pick up dings, scratches and to fade compared to a typical black Hard anodised rim.
Talk to the anodiser’s they’re normally pretty helpful, a batch is normally around £50-75 though deals can normally be struck.