There is a tall nicotiana in red. It's about 3 feet tall and there are many varieties of tall red zinnia with large flowers that come in red.

Both these are easy to grow from seed although because of their size they should be started early because they will take some time to grow in height before they flower

Oklahoma Red zinnia are wonderful and mildew-resistant. They reach 3 feet tall in my raised beds. Also, geraniums and salvia.

Although grown from a perennial corm, Lucifer crocosmia is a beautiful choice. There are heuchera (again perennial) that have lovely, delicate red flowers as well.

Here is a link that might be useful: My Garden and Oklahoma Red Zinnia

In addition to the red zinnias that have already been mentioned, there are some red celosia that are tall. Celosia come in both tall and short varieties. There are also some red coleus that can grow rather tall.

ZM

Not an annual, but monarda (bee balm) 'Jacob Cline' is what I grow as a tall red. Of course, it won't bloom continuously like a red zinnia or other summer annual.

Cameron

Dahlias. Some of the dinnerplate and decorative types get at least 4 feet tall. You can, of course, grow them as annuals if you wish, or dig and store for future years.

There are some varieties of red salvias that can get up to
30 inches tall.

Depending on how red you want your red to be (and whether it is cool or hot), you might like
Cramer's Celosia. It gives huge cockscomb like blooms in the purpley red color and grows to 2.5 to 3 feet high. It LOVES hot weather. The fact that it is a great self seeder and ridiculously easy to start from seed is a bonus.

Someone above mentioned dahlias. I am a big fan of Bishop of Llandaff. It is a beautiful crayon red with a yellow eye, and has beautiful lacy purple foliage to boot. Even if you know virtually nothing about dahlias like me, it's easy to grow.

And don't forget the old fashioned tall pentas. They are also a crayon red, and the plant is lovely and easy to grow in every way.

How about varieties of Amaranth? They self seed, and if you don't like their height, pinch them back and enjoy the foliage.

Fine Gardener had an article on a gentleman in the Catskills who let his annuals go to seed, and the Amaranth were a big part of his displays every year. Just beautiful!

Tetra Versailles Red Cosmos look beautiful. I've not grown them yet, but they're described as 3-4 feet tall. I know all the othe cosmos I've grown have been excellent bloomers and very carefree.

Martha