What is the better way to show these icons selected?

These are the icons we have made for one of the product and these ones are the finalized ones.

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But we have a problem as we are unable to get a better way to show the selected ones.

One way to do this is by inverting the colors but the issue is we have more than 50 icons overall and from the development perspective we have to provide two SVGs for a single icon to the developers which will make the app heavy.

So my problems are :

(a) Better way to show these icons(in general : icons with long shadow effect) selected.

(b) And a way to show them on the darker backgrounds

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EDIT: Thanks for the response people but this is what my concern is. It is difficult to show them selected on the darker backgrounds(keeping the opacity 90-80-70%). this is what I meant by the visibility issues.

Tried adding the white icons on the darker BG but it is not looking pleasing.

Suggest something. Even you can also suggest the way to show card(presently, we are using the gaussian blur image on the background with the black overlay of 70%).