How to tell if two colors go together?

Well, you could use this and put in your color and see what colors match it.

If you take a look at the colour wheel, you can see that colours opposite each other clash. Put them together and you have discord, like blue and orange, red and green, yellow and purple – these are all opposite to each other.

To see what colours go together is really a matter of trial and error, see which ones are easy on the eye. The colour wheel should help though. Try microsoft paint.

Nature is a good source of colour schemes. Go on Google image search and type “butterflies” or “orchids” and see what appeals. You may also have luck searching through NASA photos — try looking through Hubble pictures for dramatic colour schemes. Import the image into PhotoShop and use the colour-picker to get the hex code of the respective colours.

If you’re talking about color combinations for web page design, including text and backgrounds, it’s not just a matter of which colors go well together but which show up clearly without vibrating off the screen or just being downright illegible. Nature might put magenta and goldenrod together or ochre and vermilion on top of green, but your eyes would hurt if that were your text color scheme.

There’s also a question of mood, of the tone that compliments your subject matter, and of what sets off the images you’re displaying. It’s a matter of aesthetic judgment. Some people are really sensitive to color effects, so if you’re not good at that kind of design, perhaps you should work with someone who is.

I respectfully disagree with @lemming Colors that are opposite each other on the color wheel are called complementary colors. This type of color theory is taught in basic art classes and is used by interior designers everywhere. Complementary colors look wonderful together, especially when you are trying to create a contrast. For example Yellow and Purple or Orange and Blue or Red and Green.

This site explains the color wheel a little bit better and what primary, secondary, tertiary and complementary colors are.

Colors that are next to each other on the color wheel can look very nice too such as Blue and Green or Red and Orange or Yellow and Orange or Purple and Red

And most colors look good with either black or white next to them.

Generally colors will go well with each other if they are in the same temperature range (meaning warm or cold) if you put a warm color next to a cold color that is when things will start to look odd. Like this or this This is especially important to remember if you are pairing a color with a gray tone. A warm gray tone is a completely different look than a cool gray tone. This is true for any color, like if you want to pair 2 reds or 2 blues, make sure that they are in the same color temperature range (even if one is light and one is dark, or even if both colors are light or both colors are darker). Here is one excruciatingly bad example of how NOT to pair colors due to the mixing and matching of temperatures.

The best way to check to see if your colors go good together is to get a color sample book from a paint store and just start putting colors together. If you need more help, the paint stores will often have palettes of colors on a sheet that are pretty much guaranteed to work together. And you can ask the folks at the paint store their opinion. And if you think you have one color in mind that you like, try to find it somewhere in nature or in a magazine where it is being used with another color. Home interior magazines are really good for finding color combos that you like that also go good together.

And you can give an example of a color or a combo that you are thinking about and put it on Fluther and we can have a look at them.

Yes, like what @Jeruba said, if you are working with web design, you need to make sure you don’t pair super bright nifty colors with each other that will make your writing un-readable or appear to be moving or three dimensional. I’ve seen a lot of bad websites using lime green and bright red and black and it’s impossible to read. Don’t use this if you want people to be able to read a website.

Adding onto @Kardamom‘s excellent comments: if you can’t distinguish things like warm and cool colors or know when a color has a gray tone, you do need to consult someone.

Also bear in mind that colors don’t always appear the same on different computers. When my desktop and laptop are side by side, the colors on one screen are far bluer than on the other.

However, there are some things you shouldn’t do on any screen. (I really like this website owner, but bright yellow on beige on the home page…no. At least he’s changed the page that was primary red on primary yellow, which is what I went there to look for just now.)