I have a file that I've created in PS, and saved as a grayscale psd. When I place it into Illustrator, and try to color it, it just stays grayscale. So, to test this, I took a photo out of my library, opened it in PS, converted to grayscale and saved as a psd. I imported that into Illy, and all I have to is click on a swatch in the color pallet, and voila, it's a monochrome in color. It's a dilemma; as a fix, I opened the problem file in PS, copied it, and pasted into a new file with a transparent background. No luck; then I reopened and used the background eraser, and re-saved, still no luck. So, to summarize, I create a file in PS, save as grayscale, and it won't colorize, but if open a photo and save as grayscale, it works... my brain hurts...
Steve