Preheat the oven to 350ºF/180ºC and line a baking tray/cookie sheet with parchment paper.
Add the dry ingredients to a mixing bowl and mix using a wooden spoon or spatula.
Add the wet ingredients and mix again until everything is well combined and you have a sticky dough.
Divide the dough into 7 equal parts, then add about 1/4-1/2 tsp of food dye powder (depending on the desired color intensity) to each of the parts.
Using your hands, mix the dough and dye powders well, then separate each part into two smaller parts and form them into dough balls (don't use a cookie dough scoop as they need to be firmly rolled).
Place your 14 cookie dough balls on the lined baking tray, then gently press them down a little bit, making sure they don't get too flat. If adding sea salt flakes, you can add them now or once the cookies are baked (adding them before baking will make them stick better).
Bake the tahini cookies in the oven for 7 minutes (see notes for adjusted times if you're making smaller or larger cookies instead). Optionally add any additional toppings of your choice.
Let the rainbow tahini cookies cool for about 2-3 minutes, then enjoy with a glass of ice cold plant milk or however you desire!