The ASCOM driver might be pulling b-w because it doesn't debayer the image. We usually save that till we'll processing images.
The image just looks B&W because it hasn't been debayered. ALL images are in fact B&W from the sensor, until something picks out the red, green and blue pixels from the bayer matrix, and combines them into color pixels. In a DSLR, that is done in the camera. In an astro camera, it is not. As Raginar points out, that is done in your processing software.
I use SGP, which shows a preview of the image immediately after being captured. This shows up as B&W because SGP does not debayer the image. Some image capture software will debayer and show you the image in color. But either way, the image is stored in a file as B&W, and must be debayered by your processing software, usually during stacking.