Ooh, that's a pretty plant! I think that you need a trio of colors to make a big color splash. I'd be extremely tempted to pair it with that bright purple Gomphrena and small orange zinnia angustifolia. But that's me. These two are heat and sun tolerant annuals, requiring very little watering once established.....and no dead heading. They'll bloom until the first heavy frost.

I can't think of a chartreuse plant, at least not one that blooms for a long time....and can take the sun. Did you have something in mind?

Other good combinations with red are yellow and white, blue and white, coral and blue. I'm sure that others will come up with some great ideas. Just keep the actual performance of the plants in mind.

Ohhh, thanks! I absolutely love purple gomphrena and will try your suggestion. I can't wait to see it!

Melampodium.

tj