Make the crust first. Add the flour, sugar, and salt to a food processor.
Cut the vegan butter into chunks and add them to the food processor. Pulse for a few minutes, until the butter has been cut into the flour and the mixture resembles sand.
With the processor running, pour the cold water into the top of the processor and let process until the dough comes together in a ball. Scraping down the sides of the processor as needed.
Bring all the crust dough together into a ball, and then cut the dough in half. Put each piece of dough into some parchment paper, and then put it in the fridge for about 30 minutes to an hour.
Once you have chilled the dough, make the filling. Combine all the filling ingredients in a medium-sized mixing bowl. Toss to combine everything, folding together until the berries are fully coated in sugar and cornstarch. Making sure you don't have any dry spots.
Using an 8 or 9 inch pie pan, roll out each piece of the crust to about 1/8 inch thick circle. I like to roll out on the parchment paper, makes it easy to transfer. Place one piece of the crust in the bottom of the pie pan. Pressing it down into the pan. Trimming any excess that hangs off the side.
Poke a few holes into the bottom crust with a fork, then pour the filling into the crust and smooth it out evenly.
Transfer the top crust on top of the filling. Trim any excess crust, then seal the two crusts together with a fork, and/or fold the edges together. Cut a few slits in the top crust to let steam out.
Chill the pie while you preheat the oven to 450 degrees(F).
Bake the pie for 10 minutes, then reduce the heat to 350 degrees(F). Then bake for 15 minutes. Rotate the pie and bake for another 20-25 minutes or until the pie is golden brown.
Let the pie cool on the counter for at least an hour, then once the pie is room temperature, glaze the top.
Whisk together the powdered sugar, milk, and vanilla until smooth. Divide the glaze, using about 3/4 to make the purple glaze and about 1/4 to make blue. Whisk the food coloring into each until it reaches your desired color.
Pour the purple glaze on top of the pie and then smooth out, covering the entire top. Then, drizzle the pie with the blue glaze. it
Chill for another 2 to 3 hours, keep chilled until ready to serve!