If you are drawn to really deep red lettuces, consider Hyper Red. Selecting from a cross between Valeria, a very red cold-tolerant lollo rosso, and Wavy Red Cos, an undulating savoyed red romaine, Frank Morton bred Hyper Red to accentuate pigmentation and ruffling. The striking result tastes good with a pleasing texture. You can hear Morton talk about the breeding of this variety on OSSI's Free The Seed! Podcast.
Holds for a while in July before succumbing to heat. Good cold tolerance. No warm-temperature germination tolerance.