Try using some orange juice for Valentine hearts (pictured).
For a 9×13 use these amounts:
In a medium saucepan, before turning the heat on, mix the gelatin into 1/2 cup of the cold juice, whisk until it's all dissolved and let set for 3 minutes or so. Whisk in the rest of the juice, and turn heat on low just to dissolve and mix it all together, don't boil. Pour into your pans. If you don't like the little bubbles that will develop on top, cover with plastic wrap and refrigerate until set. Tip: first situate your pans in the fridge where they'll be setting up, and pour the gelatin in, otherwise it's tricky carrying a pan of liquid to the fridge from the counter without spilling it all over. Yeah, trust me on this.
Recipe by Kelly the Kitchen Kop at https://kellythekitchenkop.com/homemade-finger-jello/