Sometimes people wonder why the media format in which a record is viewed makes a difference. After all, isn't microfilm the same as the original? I've taken another look at the digital copy I made of my grandfather's 1903 birth certificate. All the writing appears to be the same color, but the handwriting in a couple of places is different. I'm better that the original has slightly different color inks. A color copy would show those colors and make the difference more notable.
The different writing on my grandfather's birth certificate centers on his name. It looks like he was unnamed at birth and at some point in time the last name was written in. His first and middle names are printed (the rest of the information is in script)--I'm betting that was done when he applied for a social security number, but I'm just speculating.
Looking at the original would answer the question about the different handwriting as I bet there are three ink colors on the original.
Something a black and white microfilm image hides.