Color selection is completely a matter of taste. You can have a single color or a number of colors. Patterns are also a matter of individual taste and can be concentric circles around the crystal, vertical lines, or any pattern you like. Start by painting or applying glue to the base of the crystal bowl. Do not paint the entire inside of the crystal at once unless you just want to use one color of glitter. The instructions on the glitter glue or the glitter paint will tell you how long to wait before adding glitter so you get a nice even coating of glitter with no clumps. Use extra glitter and shake out the excess after the glues is almost dry. Then do the next layer in the same manner and so forth until the entire crystal is coated inside with glitter. Glue the solar powered garden light to the plastic cover that came with the light or use another cover that fits the light and will fit into the crystal ball.
One great idea to prevent breaking the beautiful and colorful night light you made is to make a base for it. Even if the bottom of the crystal ball is flat there is a possibility of knocking the night light off of a table. This is particularly true with very young children because they will want to grab the light.
You can make a base out of a piece of wood that fits around the bottom of the crystal ball. Anchor the wood to the place you want the night light to rest with temporary adhesive, glue, nails, or screws depending on the surface of the place you want the light to stay. You might even consider making this little project into a home business. Involve your kids and make night lights for your whole town. If they cost you four dollars to make and you can sell them for $10 then you have a sixty percent profit margin less labor.