So I know it's a lot later than tomorrow but I'm getting to it.
Picking paint can be such a huge, and overwhelming task. There are so many how do you choose? One of the biggest mistakes I make is that I find a paint chip that I love and must have. I paint the room and am in love with my walls but then I can't find anything else that goes with them. Paint can be colored to match just about anything. Paint has the widest variety so don't start with paint start with something else. Start with a bed spread, couch, curtains or art piece that you will be using in the room. Match a color to one of these items. I take the color I like and go one, sometimes two shades down on mono chromatic paint chips (two colors lighter) . A small 2" square isn't a good indicator of what the color will look like on your walls. A lot of times the paint chip color comes out darker than you were thinking that is why I go two shades lighter, this means there is more white in the color. I have found that reputable paint stores are a great resource for picking color as well. I like to ask those working for advise for example, I needed a red but I didn't want a rusty shade or a pink shade I wanted a true red. I asked the paint store employee and he picked out a perfect red. If they supply to professional painters chances are they have seen the colors on walls or they have mixed enough of them to know what colors designers are buying.
There are a few things you need to know. Light in your room will change how it looks, it's best to buy a small amount and sample it. You can paint a 2'x3' piece of foam core (found at art supply stores) and move it around the room and view it at different times of day. Or different walls. I have painted rooms after dark and loved the color only to wake up in the morning and be disappointed by how it looks in the daylight. The great thing about paint is that if it doesn't work, it's not a big deal because it's relatively inexpensive to start over. Dark colors will require more coats. Plan on two coats with any color. The surface of your wall will change things also. Prep is so important, just as the foundation of a house, the better the bottom the better the top. Make sure the paint surface is clean and ready to go imperfections are only highlighted. There are whole books on how to paint and prep but I'm not going there. I hope you enjoy color in your house. You may be pleasantly surprised at the difference it makes.
End note: If you pick a paint first and go with it and can't match anything to it. Use neutrals. for example, I'm adding black and white in pictures, curtains, and bedding in my room I just couldn't wait to paint blue.