Building a Police Box a.k.a. The Doctor's TARDIS
Step 11. Paint time
Primer/sealer to the outsides and two coats of blue.
This part is best left to you. You can get all the information on the type of paint, applications etc. from your local paint stockist.
The choice of colour is also up to you. There are many different variations of blue used for both the Police boxes and the TARDIS props.
There does not seem to be a standard blue color used for the many TARDIS props, so personal preference is probably the way to go.