In a mixing bowl whisk together graham cracker crumbs and sugar. Pour in butter and stir until evenly moistened. Divide mixture among 8 - 10 dessert cups and lightly press into an even layer, set aside.
Pour lemon juice and water into a small bowl. Sprinkle gelatin evenly over top, let rest 5 minutes. Meanwhile, whip heavy cream in a medium mixing bowl until soft peaks form.
Add in 1/3 cup of the powdered sugar, tint with yellow food coloring if desired and whip until stiff (but not lumpy) peaks form (shake cream from beaters, no need to clean).
In a separate large mixing bowl whip cream cheese until smooth and fluffy. Mix lemon curd and remaining 2/3 cup powdered sugar into cream cheese mixture.
Heat rested gelatin mixture in the microwave on high power for 30 seconds. Whisk for 1 minute to thoroughly dissolve gelatin, then let cool 3 minutes*.
While mixing cream cheese mixture with hand mixer, slowly pour in gelatin mixture then blend until thoroughly combined.
Gently fold 1/3 of the whipped cream mixture into the cream cheese mixture to lighten, then add remaining whipped cream and gently fold until combined.
Spoon or pipe mixture into dessert cups over graham cracker layer. Cover and refrigerate 2 hours (or up to 1 day ahead if desired) to set. Garnish as desired. Serve cold.
Prep time includes 2 hours of chill time.
The gelatin mixture shouldn't be allowed to cool more than 3 minutes, otherwise it may start to set. Then you could end up with little lumps in the mousse.
For the freshest, brightest flavor, use freshly squeezed lemon juice.
Make sure the cream cheese is at room temperature, otherwise it won't whip up properly.