Paste this CSS code in your "Custom CSS" in Setup & Styling. Select the background-color and text color you wish with your own color code. I also did rounded corners with border-radius, if you don't want it don't include that part in your code.

.bzfy-t-feed-tile-grid .bzfy-c-tilegrid-button--dark {
    color: #000;
    background-color: #ffffff;
    border-radius: 25px;
}

Before:

After:

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