Embedding a player on a web page means that it may be affected by other CSS being called on the page. This may result in a variety of unexpected appearance modifications including the play button appearance.
When embedding a player on a user owned web page, the background of the play button may appear different than expected.
CSS being loaded on the web page is overriding the default player settings resulting in an image or different color being loaded
Carefully evaluate the CSS being added to the page (the browser inspection tool can help narrow down where the CSS is coming from) to determine which code may be affecting the player.