Great idea for a modular knit blanket. One simple shape makes a great quilt. Sidewalk Quilt by Pippa, an original design. Pattern available on her website and a similar version for sale in her Etsy shop.
I cut 10 x 5 rectangles from various red fabrics, created blocks using two different red panels, and then did a fence row-esque pattern, alternating vertical and horizontal placement. Simple straightline quilting and used strips of reds for my binding.