Watercolor paint is available in tubes or (less commonly) little pans. The plastic sets so familiar from grade school material supplies lists are not archival and therefore, generally not used by artists. This is not because artists are snobs (usually), but the pigments in these paint sets are "fugitive", which means they will fade rapidly when exposed to sunlight.
Using whiskey may have a very faint affect on your colors. Because most whiskeys are a warm golden brown, the pigments already suspended in the alcohol may mix with the pigments in your paints. This will not change the colors dramatically (blue will still be blue) but it may warm up the tone of the color slightly. If you prefer to have absolute, complete, fanatic, and verging on the totalitarian control over the color tone in your painting, may I first suggest you get over it. This is not an art form for the National Portrait Gallery. This is a casual way to pass time in a dark bar or on a candle-lit patio with friends. If I can’t persuade you to reject your insane degree of anal retention, feel free to use vodka. It’s clear (at first) and will not alter your color in the slightest.
While alcohol is often considered a preservative, this is not even close to being an archival technique.
This medium is intended to be very transparent. While white watercolor paint exists, the best white in your painting will be from NOT PAINTING the area you want to be white. That’s a challenge! Watercolor will flow freely from place to place on a soakable surface such as paper. There are masking fluids and films (Frisket) available, contact paper, or you could even paint rubber cement onto an area you want to stay white. Less successfully, white crayon will mask an area, but you can’t remove that. When paint flows into an area you weren’t intending, sop it up quickly and carefully with a paper towel.
Layering the color produces nice effects. Use a dry-brush technique on a dried area, or you can lay down a wash over an area, and let wet paint flow into the wash. Experiment. It’s fun!
Do not be intimidated by watercolor. Remember being a kid, with those little paint sets in little pans? Remember how, in the course of one painting, you would either use up your favorite color or panic as paint ran uncontrollably all over the paper, sometimes over the edges? It’s largely an unwonderful experience but that’s the part that stands out, doesn’t it, rather than the joy of creating and getting messy. Try to put that behind you, and practice trying to paint a straight line, lines of varying thicknesses, outline some shapes and fill them in; tackle some basics before you try the full blown composition. Or don’t!!! Just have fun. Don’t fuss too much about it. Just dive in and loosen up and have a little fun! That handy-dandy glass of liquid courage may assist here…
Gouache is an opaque water-based paint. It can be used interchangeably with watercolor paint, but if you want the familiar watercolor transparency, you have to be mindful about adding the right amount of water/whiskey to ensure that transparency. It’s great to use it because it inevitably gives you a chance to say the word out loud: gwaaaahhsh Fun, isn’t it?
Acrylic??? Some people choose to handle their acrylic paints in a watercolor fashion. This is fine for regular watercolor painting, but I strongly advise against ingesting acrylic paints. They are generally rated "non-toxic", but the pigments used in these paints are the same as in all other paints: some are inherently very poisonous in large doses, and acrylic is plastic. Acrylic paints are uncured plastic. Let a gob dry on an enameled metal or porcelain palette, then peel it off and you’ll know exactly how plastic this paint is. Don’t eat or drink it. Plastic is DEFINITELY not good for you.