If the node is red and the link is green with a percentage in the link is up why would the node be red?

The reason why the node will be red states that the device is down as it is monitored with SNIPS only. If the link line is green with a percentage, this is displaying how much traffic the link is doing in percentage. The link to the node will sit on a separate interface.

If the node is red and the link is red but still up, what would be the reason for this?

If the link is red and is configured to colour the link with utilisation, then this means that the link is running at high usage capacity. If the node is red with an exclamation mark on it, it means that the event source is set to any and an interface on the device is down.