In a chart, plot syle: line,  color based on: net change, time frame: one hour.  Can I write a condition to make sure the current line section is red or green?

You can just click on the chart and select Create Scan Condition to create the condition.

Create Conditions from Your Chart (5:25)

Select Moving Down Net with the Period set to 1 and Net Change < set to 0 to check for a red segment or Moving Up Net with the Period set to 1 and the Net Change > set to 0 to check for a green segment.

Note that the segment will be green when the net change is zero as well. So a Condition Formula to check for red would be:

C < C1

And a Condition Formula to check for green would be:

C >= C1

PCF Formula Descriptions
Handy PCF example formulas to help you learn the syntax of PCFs!