Root damage explanations

[Zaskia]

Hi, I've tried looking around the site and using google but I always end up with the wrong search results. Could someone explain the following to me please? I'm trying to understand how the roots work in these two instances.

If a root has a break but is still connected by the inner thread:

How does that affect the end part of the root?
Will it slowly die off?
Can it still do its job properly with regards to water/nutrients?

If the roots are firm but yellow/cream/very light brown and not becoming green at watering:

How unhealthy are they?
Can they revert back to the usual silver/green?

Thanks!