Colour changing gin is a plain gin infused with dried blue pea flowers. Nothing artificial is added, and the pigment shifts from blue to pink with an acidic mixer.
Compound gin steeps juniper and botanicals in a finished spirit instead of redistilling them, which is why it carries colour and why you can make it at home.
Making gin at home needs no licence, but selling it needs one from your council under the Licensing Act 2003, and producing for sale needs HMRC approval.
No licence or HMRC approval is needed to steep botanicals in a spirit you have bought. Producing alcohol and selling it are the two things that do need permission.
Infusing botanicals into shop bought vodka is legal and needs no licence. Distilling your own spirit without HMRC approval is an offence. Here is where the line sits.
Retirement gifts that ask something of them: country wine over eight to twelve weeks, dry cured bacon in a week, and ten fresh cheeses in an afternoon.