The traffic lights
| Colour | State | Meaning |
|---|---|---|
| 🔴 Red | Not configured | The node needs settings before it can run |
| 🟡 Yellow | Configured | Ready, not yet executed |
| 🟢 Green | Executed | It has run and holds output data |
That status bar under every node is the fastest diagnostic in KNIME. A workflow of forty nodes tells you at a glance exactly where it stopped.
Red is usually not an error
A newly dragged node is red because you have not opened it yet. It is only a problem when a node that was working turns red — which usually means an upstream column it referenced has been renamed or removed.
Hover over a red node for the reason. The message is generally specific: column 'Revenue' not found in input table points straight at the cause.
How execution propagates
Executing a node executes everything upstream that it needs. So you can work on the end of a workflow without manually running each earlier step.
Changing a node's configuration resets it and everything downstream to yellow, since their inputs may now differ. That reset is correct behaviour, and it is why a small change can mean re-running a long branch.
Failures
A node that fails execution shows red with an error triangle. The Console gives the stack; the node's own tooltip usually gives the readable version.
The most common causes: a column renamed upstream, a type mismatch, or a missing value reaching a node that cannot handle one.
Reset
Right-click → Reset clears a node's output and everything downstream, returning it to configured. Useful when you want to force a clean re-run rather than trusting cached results.