Roundal, are you considering a colour change???
Your E39 looks great in that colour! Just my thoughts - if you'd like one in another colour, maybe look out for another one in that colour at a good price. Then you'd have two different coloured E39s to enjoy!
Changing the colour of a car is just so much work - inside, out, door jambs etc. It would cost a great deal and won't be worth it on the long run. (imo)
BTW, I have seen only one Calypso red E39 not far from my home - the E39 in Calypso red is truly elegant indeed, but more Jaguar like elegance. Silver is more BMW like - a mix of sporty, elegant and techno!
Respraying the same colour is fine - but changing? I am not too enthusiastic about that!
I did a colour change on my E34 but that was because I had months to work on the car and the car is just an extra car I have. And, no labour cost as I did it myself.
Your E39 is perfect in that original colour!