There is a cultivar called 'Ruby Slippers' that is a deep wine color.
The color was too dark and saturated to be seen from far away, it just disappeared. So I moved it to the patio wall where I see it up close and can marvel at the velvety rich hue.
But the cardinal red species is an eye popper even from far away in my back garden. I need more of these to make a bigger impact, but they are hard to locate at local garden centers. No one carries them, although the center I went to last week will order them for me. My small stand isn't big enough to divide yet.
They want full sun and very moist, wet soil. Mine get some late shade under a large maple, but they do see the sun most of the day. The area of the back garden where I have them planted is damp, but when hot dry summer bakes the soil, I water the cardinal flowers frequently.
I don't know why local centers don't have them in stock routinely. Lobelia cardinalis is the kind of plant that would tempt anyone shopping for color, tall structure and hummingbird magnets in their gardens.