you can check this workflow example on how to color your Bar Chart (and more!):
Couple of notes/suggestions:
before opening a topic you can do a quick search of KNIME Forum (search button is in the right upper corner) for existing topics while on KNIME Hub you can search for workflow examples
you are opening topics in KNIME Development category which is for (new) node/function development within KNIME. Not a big issue but would be better to choose proper one (for general questions around KNIME and workflow development KNIME Analytics Platform category is the one)
although wouldn’t help in this case KNIME Docs are also great resource