Hey there fellow Tardis builders
does anyone have a reasonable idea as to which shade of blue that i can use on my Capaldi box as i cant seem to find anything on any other topic.

This is a tricky one as the TARDIS has (once again) changed color since her 2010 "regeneration" after the 10th-to-11th Doctor's explosive regeneration damaged her. She originally looked "stained" with that wood grain showing through what was said to have been "Subaru Blue" spray paint. Over the next few years the wood grain became less apparent, and the blue became more "blue".

Now that Capaldi is at the console the Old Girl looks almost Royal Blue - very close to what my 1972 VW Karmann Ghia looked like when I first got her, and her paint was still relatively fresh (only about six years old, but well taken care of). The TARDIS is really bright (at least in Series 8 and 9); not light blue like in "The Three Doctors", but a rich, erm... heck, Royal Blue is the only thing that comes to mind. At least that's how she looks on my telly, and on the computer screen in the publicity photos I've seen.

I'm sure others will have a better name for the color, but when all else fails, you can't go wrong with a good Royal Blue.

Dino.

Somewhere, the BBC declared what was "Official TARDIS Blue."  Of course who's to say they actually used Official TARDIS Blue for the Capaldi box, so there you go.  
https://s-media-cache-ak0.pinimg.com/236x/3e/df/fa/3edffad6a5667dfcac9bd368480cb86d.jpg

Thanks for the help, i saw the pics of the Tardis miniatures being made on another thread somewhere and saw the paint code was pantone 654c which is pretty much the same as the "official" colour so i think i will be using the pantone 654c for my box.   

Blue is tricky anyway.  It can look totally different in different light and at different times of the day, so while many people obsess about getting EXACTLY the right color, personally, I think getting close is good enough.  Some days it will look exactly the way you want it and some days you'll hate it no matter how perfectly you pick. 

Didn't Rubbertoe workshop pictures reveal the pantone code for the TARDIS blue used on the smaller versions in "Flatline"?

For the Flatline mini TARDIS it appears to be Pantone 654 C as indicated on the bottom right hand corner of the blueprint. Taken from the Rubbertoe Replicas Facebook page.

Great work, one question, What does it say on your drill box ?