Unfortunately, fluorescent or neon colors such as hot pink, lime green, day-glow yellow/orange, or vivid tangerine, can't be mixed from the standard primary colors -- blue, yellow, and red. You have to buy fluorescent colors ready made, or be satisfied something that's a strong, saturated color but doesn't "pulsate" quite like a neon one.
Various paint manufacturers produce fluorescent colors. Have a look in a large art supplies store, or an online art store (though computer screens don't really do fluorescent colors justice).

