See the image for better understanding.

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The light bulb icon is a hint annotation, and the hints displayed/marked are controlled in Tools > Options > Editor > Hints. Select the appropriate language and uncheck those hints you don’t want displayed.
The green icon is an override annotation. it indicates that the function/method in the child class overrides one of the same name in the parent class. Annotations, in general, are formatted in Tools > Options > Fonts & Colors > Annotations.
(Note that the light bulb hint annotation is just another annotation.) I am not familiar with a way to turn off these annotations, or a way to turn off annotations in general.