JUCE v6.0.1
macOS 10.15.6
The following code:
void MainComponent::paint (juce::Graphics& g) {
const auto redColour = juce::Colour (0xffff0000);
g.setColour (redColour);
g.fillRect (getLocalBounds());
auto attributedString = juce::AttributedString ("hello colour");
attributedString.setColour (redColour);
attributedString.setFont (juce::Font (200));
attributedString.setJustification (juce::Justification::centred);
attributedString.draw (g, getLocalBounds().toFloat());
}
produces the following result: