I am looking for a paint that will go over exterior window red tile sills. I would like a bluey grey colour as close in colour to the blue/grey bricks that are used please. Could you advise on what I could use please?

Assuming the red tiles are ceramic, they are clean, dry, sound and prepared as detailed in the technical data sheet we can recommend Zinsser Bulls Eye 1-2-3 followed by 3 coats of Zinsser Allcoat Exterior (Water based).

This is available in many RAL, NCS or BS colours in a matt, satin or gloss finish.

We would recommend viewing a physical colour chart to choose a suitable match.