The hardware test phase is 'orange' when it fails with a warning. These warnings occur when a test passed with warnings or after retries. They can also occur with the tests are aborted (see below).
To test whether your change breaks an incremental build, you will need to create a pristine local checkout, build it, and then add your change and verify that your change does not break anything. First you will need to find a builder to run both your tests on so that you can test a build. These are listed under "Buildslaves" on this page: http://chromegw.corp.google.com/i/chromiumos.tryserver/builders/x86-generic-paladin
Once you have found your builder, you can run your test. I have given an example below with a 'buildXX-m2' placeholder, but please replace this placeholder with the build slave you would like to use.
From the documentation in cbuildbot_config.py: If important=False then this bot cannot cause the tree to turn red. Set this to False if you are setting up a new bot. Once the bot is on the waterfall and is consistently green, mark the builder as important=True.
If you are a Googler, you can use gs://chromeos-throw-away-bucket for testing. Keep in mind that the contents can be read or deleted by anyone at Google.
We also have another similar bucket named gs://chromeos-shared-team-bucket . Probably using gs://chromeos-throw-away-bucket makes more sense since it is clear that the contents there can be deleted by anyone at Google.
If you are not a Googler, you should create your own bucket in Google Storage.
Emerge will tell you what USE flags are used when the -pv flags are provided e.g.
FAQ items covering general development questions
What should I read first/Where do I start?