What is the opposite of highlighted, in a visual presentation

single-word-requests

I've mostly heard of lowlights in terms of sports events or careers

However while trying to find references for that meaning I found one to do with hair colouring

Lowlights versus highlights

Lowlights involve darkening strands of hair by using colours that are darker than your natural colour. In contrast, highlights use colours that are lighter than your natural shade.

So if the negative highlighting you are doing involves shading (bright vs dark) rather than changing the colour, I think lowlight/lowlights/lowlighting is perfect.

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