The colors you're describing follow the same pattern as BSF eggs which they most likely are. It takes about 4 days for them to hatch. I would guess that you've already had some hatch but the new grubs are still so tiny that they can't be seen in your photos above. I'm pretty sure that within a week or two you'll be seeing thousands of new BSF grubs.
Here's a photo that shows the color variations of BSF eggs as they age:
