E INK is directly selling a 31.2 inch Triton e-paper screen. It utilizes a reflective electrophoretic technology display module based on TFT active matrix with color filter design. The resolution is 2560 x 1440 pixels, the display is capable to display 4096 colors depending on the display controller and the associated waveform file it used. There are a few applications that can be selected during checkout, such as the screen and board they are optimized for e-readers and also enotes.
This screen and board are very expensive, you are looking at forking over $2,300 USD. This is the only E INK Triton development kit they are currently selling and there is nothing smaller available.
If you are looking for a modern color e-paper, E INK stated they will launch Kaleido development kits to their site sometime in 2021, but no timeframe was announced.

Michael Kozlowski is the Editor in Chief of Good e-Reader. He has been writing about audiobooks and e-readers for the past ten years. His articles have been picked up by major and local news sources and websites such as the CBC, CNET, Engadget, Huffington Post and the New York Times.