<?php

$colors = array("White", "Blue", "Black", "Red", "Green");
$coloredCards = array();
foreach($colors as $color) {
    foreach($coloredCards as $existingCombo => $existingCards) {
        $newKey = $existingCombo . "-" . $color;
        $coloredCards[$newKey] = json_encode(explode("-", $newKey));
    }
    $coloredCards[$color] = '["' . $color . '"]';
}
var_dump($coloredCards);