Photos Markup facility

iPhone 15 using iOS27.0.

Why does the marker tool only result in 'wash' effect with any colour other than black or white?

Even 'pure' primary colours (rated at 255 for that colour, with the other at 0) display the ‘wash’ effect.

Any colour other than black or white shows what is being coloured over underneath that colour.

Any advice would be appreciated.

Thanks.

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