Best icing for fine detail please?

[Igneococcus]

I'm making an Eeveelution cake for ds' 9th birthday and I need to buy/make icing that allows me to do fine detail.
I found cookie cutters on Etsy for Eevee and its evolutions, they are the sort that imprint the motive on top of pastry. I want to make mint creams, because ds loves them and I think that they will show the detail better than if I bake biscuits but I need some icing to colour them in.
Does anyone have recommendations for icing that is easy to apply and not runny?

Royal icing if you make it thick enough.

Royal icing (you can buy royal icing sugar rather than using rgg whites to make it easier) and use proper paste colours rather than cheaply liquid food colours.

Can I get royal icing sugar at normal supermarkets? And do I just add water very carefully to get the right consistency?
Any recommendations for a good online supplier of paste colours?
Thank you very much for your help.

Yes, you can get it in most big supermarkets. I normally use Wilton or sugaflair colours which you can get in Lakeland and Hobbycraft.

Forgot to say, it has instructions for how much water to use. You have to beat it for a while though so I'd recommend an electric mixer.

If you need white icing, use lemon juice instead of water also. It makes it whiter.

Thanks purpledaisy. I'll have a look on the Lakeland site.

I didn't know that gretchen I always thought you add lemon juice to make icing taste nicer. Thanks.

No problem at all.

This site is really good for supplies too-I've used them a few times and they're quick with delivery and helpful if you've got questions.
www.cakecraftshop.co.uk