Plastic Logic - the maker of flexible e-paper - has shown off an e-paper smart watch concept with a difference: this one's in colour.

The concept isn't the complete dynamic colour solution like the company's colour e-paper, however, because this smart watch prototype uses instead simple colour filter overlay where a wide spectrum of colours can be positioned according to an individual product's design.

READ: Plastic Logic demos colour video playback on e-paper

The initial design is to illustrate that colours brighter and more vibrant than those in a typical e-paper colour solution - such as Platic Logic's own 4,096 colour solution, mentioned above - can be displayed via this simple solution.

The working model we saw revealed colours as bright only when the e-paper display behind dropped out to its lightest grey. For devices where there's a single display area with a binary on/off use - such as a battery life display, heart rate green-through-red warning light, or such other such display functions - it makes good sense.

The areas of the device not covered by the positioned colour filter reveal themselves in the same was as the usual e-paper, which means they can dynamically display whatever they're told to. That's all down to possible future product development.

We've previously seen e-paper smart watches in abundance. There's the well-known Pebble, as well as the super-slim CST-01 E Ink watch which Pocket-lint saw at the Consumer Electronics Show 2013 in January. But neither of these offers up colour to tickle those rods and cones.

READ: CST-01 E Ink watch hands-on

As Plastic Logic isn't a watchmaker, this is just a window into the could-be future. As you can see from our pictures the super-slim device - less than 1mm thick - is undoubtedly teeny. Around the back things are a tangle of wires and silicon for the time being, but that's where a designer could come in to finalise such a concept.

The addition of a battery, NFC Bluetooth, Wi-Fi functionality, front-lighting like that of the Kindle Paperwhite - as otherwise the watch would be next to useless in the dark - are all things that could be added to make up for a more complete device, among plenty of other ideas.

It all depends on those creative manufacturers out there, for now this prototype is just an interesting concept to show off Plastic Logic's e-paper technology and how sometimes a simple, cost-effective solution could be the future of affordable yet slim and stylish wearable tech.