Do you live near a library? Check the gardening and landscape sections for the many books that deal with this subject. There are too many for me to list here. Pamela Harper has written several describing which colors to plant together. What you need to know as well are the amount of sun, shade, type of soil, moisture etc. that your plants need, and plant ones that have the same requirements together. That's more important than deciding which colors go well together. You can use the internet to search data on each of your plants and make some notes on each of them as to what conditions they prefer. I use "Google" with the scientific name of the plant and then summarize the info. on a paper where I have all my plants listed. That way I know the ultimate height and width of the plant, whether it prefers sun or shade, etc. Then I have all the info. I need to decide where to put it in my garden. On your paper list you should have marked color and blooming time as well, whether it is a shrub or perennial.

I like nausturtiums because they are a trap crop and the deer won't touch them. But unlike some trap crops, like radishes for flea beetles, aphids on nausturtiums act as a reliable food source for predatory insects like ladybugs, which then also attack the aphids on the tomatoes, keeping their numbers from exploding. I don't believe that any companion plant will drive off pests from near by plants, it just doesn't make sense that a 2 ft tall companion plant at the base of 6 ft tall tomato plant will scare off a nearly microscopic bug, nature just doesn't work that way for things trying to scratch out a living. If you had tall marigolds enveloping short lettuce it might be a different story. Queen Anne's Lace (Wild carrot) is a wonderful companion plant in that it doesn't have to be next to the target plants, just in the area (and once established it grows striongly and self seeds the second year and after). It grows as soon as snow starts to melt and blooms early in the season to draw in ladybugs and hoverflies while the tomato plants are still little. Nausturtiums take forever to grow. but are large enough by the time the QAL dies back. As I said, my hungry deer won't touch either of them.

There's a lot of confusion over the terminology here. Merely planting one crop next to another isn't companion planting. Intercropping isn't the same as companion planting. Nor is successional sowing. Nor is catch cropping. jolj's example would count as catch cropping. The plants do not have an effect, real or imagined, on each other. intercropping, catch cropping and companion planting

English - is a dreadful language (humor ahead and it is long) We'll begin with box, and the plural is boxes; But the plural of ox should be oxen, not oxes. Then one fowl is goose, but two are called geese Yet the plural of moose should never be meese. You may find a lone mouse or a whole lot of mice, But the plural of house is houses, not hice. If the plural of man is always called men, When couldn't the plural of pan be called pen? The cow in the plural may be cows or kine, But the plural of vow is vows, not vine. And I speak of a foot, and you show me your feet, But I give a boot - would a pair be called beet? If one is a tooth and a whole set are teeth, Why shouldn't the plural of booth be called beeth? If the singular is this and plural is these, Why shouldn't the plural of kiss be nicknamed kese? Then one may be that, and three may be those, Yet the plural of hat would never be hose; We speak of a brother, and also of brethren, But though we say mother, we never say methren. The masculine pronouns are he, his and him, But imagine the feminine she, shis, and shim! So our English, I think you will all agree, Is the trickiest language you ever did see. I take it you already know Of tough and bough and cough and dough? Others may stumble, but not you On hiccough, thorough, slough, and through? Well done! And now you wish, perhaps To learn of less familiar traps? Beware of heard, a dreadful word That looks like beard and sounds like bird. And dead; it's said like bed, not bead; For goodness sake, don't call it deed! Watch out for meat and great and threat, (they rhyme with suite and straight and debt) A moth is not a moth in mother. Nor both in bother, broth in brother. And here is not a match for there. And dear and fear for bear and pear. And then there's dose and rose and lose -- Just look them up -- and goose and choose. And cork and work and card and ward, And font and front and word and sword. And do and go, then thwart and cart. Come, come, I've hardly made a start. A dreadful language? Why, man alive, I'd learned to talk it when I was five, And yet to write it, the more I tried, I hadn't learned it at fifty-five!