Help Email Icon Color Change and reset question

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My stock email icon, which launches my Verizon.net email, suddenly changed to a black square. About a half hour later, it went to a blue square, blending into the stock background (with the hot air balloon). I cannot figure why this happened or how to reset the icon...any suggestions?

If I have to reset the phone, I have not done this recently. So, on the Verizon S4, is this fairly easy? Do I need to call Verizon? Is it simply a matter of selecting options and reentering basic info like Google name/pw, etc?

Thanks.