I've had a look through the reference section of the IOM15mil Group
website which includes details of liveries and paint suppliers, but there is nothing for a blue
Cale, unfortunately. If Accucraft can't remember what they used then you will have to resort to some of the measures suggested above, I fear. I think Accucraft have used car colours in the past, so a visit to Halfords or similar might be worth trying. I have (very) limited experience of using rattle can paints on live steam locos, having repainted the smokebox on my Accucraft
Peveril a couple of times. Halfords paints seem to endure the heat successfully, while other makes (and I'm afraid I can't remember which ones) go soft when hot -hence the need to do the job twice!
Neil Robinson, who posts occasionally on here, turned out a previously blue
Cale in BR-style lined black. I can't recall if he did a build log of the project, but it would obviously be quite an involved process.
Sorry not to be any more helpful.