Select vibrant veggies: spinach for green, beetroot for red, carrots for orange, and purple cabbage for blue.
Wash vegetables thoroughly, peel if needed, and chop into small pieces for easier processing.
Blend vegetables with a little water to create a puree, or use a juicer for a smoother liquid.
Strain the puree through a fine sieve or cheesecloth to extract the concentrated juice.
Simmer the juice on low heat to reduce and concentrate the color for a richer hue.
For variations, mix juices (e.g., beetroot and carrot for a reddish-orange) or add acidic/alkaline agents for shifts.
Pour into airtight containers and refrigerate; use for cakes, frostings, or beverages within 1–2 weeks.