Hello James,
I did a complete color change (interior as well) when my 113 was restored; from 050 White to Signal Red. I did this because at the time, I had no intent on showing the car thus was not concerned with 100% correctness, and I concluded that since so much was invested in the restoration, it d&^% well be something that I love. Nothing to me says "WOW" like a shiny red convertible. You've no doubt heard the terms "Resale Red" or "Arrest me Red", so you get the idea. Some thoughts of mine for you:
1) To do it correctly means interior removal as the dash must be done as well, as Tom as noted.
2) To do it REALLY correctly, you must remove darn near everything as the original factory color is on, in and underneath everything. My car was down to the shell, quite literally.
3) "Correctness" is a relative term; you probably don't want to deviate from a legitimate color for the year your car was produced. However if you have no plans to sell the car, and are creating something you want to enjoy, well the decision is entirely up to you.
4) Ensure you have a color combination (interior/exterior) that works; one that was probably available. There are quite a few sources the least of which is this forum that will help you determine which combination is legitimate.
5) As I found out in my restoration, while there are/were many interior colors made, about the only one whose detail parts (such as door pulls, ash trays, etc.)are still available is black. And yes, you guessed it, my interior went to black during the color change--not only that red/black is a subjectively nice and correct combination, but because some things I needed were only in black. My car was a basket case prior to be hauled in (goodness knows it wasn't drivable) for restoration.
6) You say you like the blue, but are not crazy about it. You might have a change of heart with a new paint job in the same color. It's astounding what a new and good paint job will look like. You might end up loving it.
7) Cost. Joe's Autobody down the street is certainly capable of painting your car...but what kind of paint do they use? If you want true MB paint, there's Glasurit and one other whose name escapes me. The paint materials for Glasurit are astoundingly expensive. To paint my car in 2001, (not including the hard top which sits unrestored in my basement...)required about $1,200 worth of paint, reducer and solvent alone. That's just the materials cost! I would guess that a metallic would have been even more.
Hope this helps!
Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored