Drawing applications (Photoshop, etc) have long supported an "Eyedropper" tool, which allows the user to select a drawing color by invoking the tool then clicking on any pixel within the document and/or screen to sample the color for use in subsequent actions.
HTML supports <input type=color> as the web platform API for presenting color selection UI. User agent typically present this as:

A "well" or small clickable control displaying a current color
When clicked, a platform-specific popup presenting ways of selecting a color (e.g. from a set of swatches, HSV/HSL gradient, RGB sliders, hexadecimal input fields, etc) 

Some platforms (MacOS) include an eyedropper within the popup UI, but this can't be launched directly (to match the behavior on native apps) and is not available on all platforms.


 

Drawing applications (Photoshop, etc) have long supported an "Eyedropper" tool, which allows the user to select a drawing color by invoking the tool then clicking on any pixel within the document and/or screen to sample the color for use in subsequent actions.

HTML supports <input type=color> as the web platform API for presenting color selection UI. User agent typically present this as a "well" or small clickable control displaying a current color. When clicked, a platform-specific popup presenting ways of selecting a color (e.g. from a set of swatches, HSV/HSL gradient, RGB sliders, hexadecimal input fields, etc) 

Some platforms (MacOS) include an eyedropper within the popup UI, but this can't be launched directly (to match the behavior on native apps) and is not available on all platforms.