It looks like the read noise changes with what ISO you have the camera set at. Take a look at this thread, which gives you some idea of the read noise of the T1i.
You don’t really have to enter the read noise. All it is used for is to determine the “ideal exposure time” calculation that SGP displays in the camera stats. I’ve never found the “ideal exposure time” to be very accurate or realistic. The read noise parameter has nothing to do with displaying the image.
Can you post a raw image file so I can take a look at what you’re seeing?
SGP displays images in monochrome so you won’ see any color.