Perilla will do well in a hot climate. So will amaranthus. Both attract grasshoppers, so remember - you've been told! Both are pretty, however, and both can become weeds if you don't stop them self-seeding.

You could try purple sage - tinges of purple, very pretty. Also look for ornamental kales (which are edible). Very nice as a border.

Herb Robert has interesting foliage, can be green with red stems, or rusty red.

Certain species of Rosella (members of the Hibiscus family) have purple foliage.

Look for Bugle, a colourful ground cover.

Beetroot leaves often take on a purple colour.

Try varieties of lettuce - you can get reddish-brown ones and purple ones which are very attractive.

Plant some garlic chives or onion chives - both have purple flowers. Catnip also has prolific purple flowers.

You might not want to restrict yourself to red or purple. Other colours can give a great contrast to just green.

Have you thought of something like a golden oregano? The colour is stunning amongst a lot of greenery. Like any oregano, it will spread if you don't watch it, but I've never found it too dreadfully aggressive.

Take a look at Ginger Mint - striking variegated yellow/green leaves.

For colour in my all-herb garden, I've got nasturtiums and chillies. Those chillies are great for colour - you get green, yellow, orange and red all at once, and in my subtropical climate they fruit all year round. You get get varieties with deep purple leaves. The nasturtiums of course have brilliant colours - I get deep red, orange, yellow. You can train nasturtium up a trellis for a great splash of colour.

Also think of silver plants, like Santolina, Lambs Ears, or wormwood, or a curry plant.

You could also consider red orach. I'm growing ruby chard which is red-veined this year among my border plants (or you could try 'Bright Lights' which is a mixture of colours) but I think it may be prone to bolting in hot dry weather.

lori
does the red orach have about the same season as spinach? It looks lovely and I'd love to have it, but I'm afraid its too late to plant it here in NC. Perhaps in the fall. I grow the bright lights chard along the front of one of the vegetable beds already.
daisyduckworth
I hadn't thought to put the hot pepper plants in the herb garden, but that will be just lovely. I have nasturtums and a yellow lemon thyme, lambs, and there's already too much sage to add any purple sage. I wish I had room to put my lettuces and beets in the herb garden, but its just not large enough and the soil is rather poor.
I am going to try the shiso and put in my small chiles.
thanks

Chard doesn't bolt, its biennial so a 2 year plant will run to seed.

My "contrast" plants are silver (curry, artemesia, silver thyme, lavender)
gold (gold oregano, gold-tipped marjoram, gold oregano thyme)
blooming (clove pinks, bee balm, marigolds, creeping thymes)

There's probably more but that's a good start. Last year I planted the purple potato vine to twine in and around the edges to give a nice contrast. I liked it, it rooted easily so one plant was quickly twenty. I was a twerp and didn't bring in any for the winter. Probably just as well since my cats kill indoor plants. I've steered clear of the purple basils because they don't seem to do as well for me as the green ones in terms of growth and flavor.