I'm not exactly sure how they classify a "Small amount" of CFL's but supposedly with fewer cfl's the spectrum matters less. I think you could grow under one spectrum, but your results would probably be better utilizing both red/yellow and blue spectrums.. The 6500k (blue spectrum) light is good for vegetative growth because it mimics the early growing season with a lot of bright sun for long hours. The 2700k is good when you go to 12/12 for flowering because it is more similar to the fall months when the days get shorter and it's nearing harvest. The sun puts off both spectrums through the whole growth period though so it doesn't hurt to have a couple of the veg lights during flower and vice versa..
So, it's possible to grow under one spectrum, but I would guess you'd get better growth and yield using both spectrums.