In Modo we can check "show clipping" in the render window to show a line hatch over blown-out highlights. I've seen more obvious implementations but it's better than nothing. Is there a way to achieve this in Octane?
OCIO will allow the usability of a false color (through an OCIO package that includes one, such as Filmic by Troy.S or custom ones). I've demonsrated it here. Look for the titled section: "Alternative to the requested ̶H̶i̶s̶t̶o̶g̶r̶a̶m̶ ̶ Waveform monitoring scope".
Be aware: long story short, nothing is "clipped" or "lost" when rendering out EXRs, or when viewing through Octane's frame buffer. For more explanations: