Preheat your oven to 350°F (175°C).

Line 3 cupcake tins with 30 paper liners.

In a medium bowl, combine the sugar and lime zest. Mix with your fingertips until the sugar is moistened and fragrant.

In a large mixing bowl, cream together the butter and lime-scented sugar on high until light and fluffy.

Add the eggs one at a time, mixing well after each addition, then add the vanilla extract.

In a separate bowl, sift together the flour, baking powder, baking soda, and salt.

Alternate adding the dry ingredients and buttermilk into the butter mixture, mixing until just combined.

Fold in the shredded coconut.

Fill each cupcake liner to the top with batter.

Bake in the preheated oven for about 20 minutes, or until a toothpick comes out clean.

Cool the cupcakes in the pan for about 15 minutes before transferring them to a wire rack.

In a saucepan, bring the sugar, zest, and lime juice to a boil. Remove from heat.

Whisk about one-fourth of the hot juice mixture into the beaten egg yolks.

Combine the egg yolk mixture back into the remaining hot juice mixture, whisking constantly.

Cook the mixture over medium heat until thickened, about 10 minutes.

Remove from heat and add the cubed butter, whisking until melted.

Color the slime with gel food coloring as desired.

Chill for at least 3 hours.

Cream together the cream cheese, butter, vanilla extract, and lime zest until fluffy.

Gradually add the powdered sugar until the frosting is smooth.

Add more gel food coloring to achieve desired color.

Hollow out the center of each cooled cupcake and fill with the slime filling.

Pipe the frosting on top to cover the filling completely.