Sorry to bother you again 1998 Ford Contour

I have checked everything on my car from fuel filter and the car is getting gas could the coil be bad or not generating enough power for it to hit? I am also on my third battery the last two where bad, but I believe this one is ok. I have checked the timing belt intact and tight, I don't have an air filter in right now, but I have checked the spark plugs and spark plug wires my neighbor said that when he checked the coil it should a clear spark not a blue one and it should be blue is this correct?