Line a flat baking tray with baking paper. Arrange 12 cups or moulds in a single layer.
Mix strawberry red layer in first bowl. Stir yogurt, diced strawberries, honey, vanilla, and lemon juice until combined. Taste and adjust.
Mix vanilla white layer in second bowl. Stir yogurt, honey, vanilla, and salt until smooth. Taste and adjust.
Mash blueberries roughly in third bowl. Add yogurt, honey, vanilla, and lemon juice. Stir until combined and deeply coloured. Taste and adjust.
Spoon strawberry layer into each cup filling one third of the way. Level surface with back of spoon. Tap cups firmly on counter.
Freeze tray for 20 to 30 minutes until first layer is partially set.
Spoon vanilla white layer over partially frozen red layer filling another third. Level surface. Tap cups again.
Freeze for a further 20 to 30 minutes until white layer is partially set.
Spoon blueberry blue layer over partially frozen white layer filling cups almost to top. Level surface.
Press fresh strawberry slices and blueberries gently into surface. Add sprinkles or granola if using.
Cover tray loosely with cling wrap without touching cup surfaces.
Freeze for minimum 3 hours or overnight until completely solid.
To serve from paper cups, peel paper away. From silicone moulds, push up from bottom. From jars, serve directly with a spoon.
Serve immediately straight from the freezer.