Hi Mum2 willie,
Things that can cause blood in diarrhoea include:
- anal fissure(cut) from the stress of the diarrhoea
-dyssentry - a disease caused by protozoa (usually in countries with poor hygeine and ingesting contaminated water)
- gastric ulceration

You said the blood is bright red, which indicates possible bleeding from lower in the tract giving fresh blood. My first thought would be stress bleeding from the anal region/rectum. I agree with what has already been said, take bub to emergency. diarrhoea and bleeding is cause for concern in the newborn especially if you don't know what's causing it.