Not really. A color sensor has a filter in front of it (usually a bayer filter) which lets each pixel capture one of the R, G, or B colors. The final image is [demosaiced](https://en.wikipedia.org/wiki/Demosaicing) and has a drop in sharpness as a result.
Pentax seems to be omitting the color filter on the sensor rather than just squashing the read out to greyscale so this sensor should be sharper than a similar color sensor.