Edmond Briottet Liqueur de Thé Vert Hibiscus (Green Tea & Hibiscus)

Bought for the wife so she can make her own 'Thyme for a change' gin cocktails which she gets from a local pub (rhubarb and ginger gin, this, lemon juice, syrup, elderflower tonic plus sprig of thyme and a piece of lemon peel). She loves them and this. Missing something to add a purple layer to the drink to finish off but local pub won't tell us what it is (it's a secret mix of something).