Ok, so the underlying sensor is the same, however on the colour there is a colour filter array which means there is a colour filter in front of each pixel (Bayer matrix) with the result of 4 pixels used to map the colour (2 greens to best replicate our eye's higher sensitivity to green). So effectively each pixel (when pointed at a white target) only receives that part of the spectrum. So while the underlying sensor has the same sensitivity, the colour camera's pixels are effectively only sensitive to one colour. This results in (and there are some software tricks involved to improve this) a lower resolution and a lower per pixel sensitivity to white light (for guiding most stars are "white" or close enough for this purpose). Check out the link below as they explain it better than I can:
https://photographingspace.com/colour-vs-mono-camera/
For planetary colour may be better, for guiding mono is preferred, you may want to calculate your pixel scale to make sure your pixel size is in the ideal range for your scope so you are not over or undersampling. I would recommend 2 cameras one for each purpose if the budget allows. I know there are some Skyris cameras, with Sony CCDs on sale at bintel at the moment.
