Images that fail contrast

Hello

I have three questions

1. if an icon (such as google material icons) is used as a label for a button, for example, a trash can for ‘delete’, does this count as text? Should it come under ‘non text contrast’ or ‘colour contrast’
2. If an icon is used as a label that isnt a standard icon and does not have an obvious corresponding word so that voice activation users would know how to reference it by name, does that come under labels and instructions? Or non-text content?
3. If a background image of an icon is used as a label for a button, and the button does have an aria-label, I would assume this still comes under non text content, as when the CSS image is not displayed, the information isn’t there for low vision users. But would it also fail contrast guidelines? Images of text do, but this is an image of an icon...

Thanks

Sarah

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