Preheat oven to 375ºF (190ºC).
Spread the phyllo dough apart using your fingers. Place dough in a large bowl.
Melt butter. Add coloring to the butter and mix.
Pour butter over the phyllo and mix with your hands tearing the phyllo. Saturate the topping in butter. (Use gloves to make sure you don't dye your fingers!)
Cover the bottom of the tray with the phyllo dough topping (minus a handful to place on top).
Drain the cheese and squeeze out as much water as you can. Press the cheese into the tray on top of the dough. Add the last handful and spread thinly over the top.
Bake for 15 to 20 minutes (the cheese will have melted).
Remove from the oven and flip tray into a slightly larger tray/plate.
Pour sugar syrup over knafeh. Sprinkle with crushed pistachio nuts.
Serve immediately.