Color sorting code

The snippet below came from somewhere on the Internet that I haven't kept track of.

for (var i = 0; i < colors.length; i++) {
        colorToCluster[colors[i]] = [colors[i]];
    }

// Merge clusters, starting with lowest distances
    var lastCluster;

for (var i = 0; i < distances.length; i++) {
        var color1 = distances[i][0];
        var color2 = distances[i][1];
        var cluster1 = colorToCluster[color1];
        var cluster2 = colorToCluster[color2];
        if (!cluster1 || !cluster2 || cluster1 == cluster2)
            continue;

// Make sure color1 is at the end of its cluster and
        // color2 at the beginning.
        if (color1 != cluster1[cluster1.length - 1])
            cluster1.reverse();
        if (color2 != cluster2[0])
            cluster2.reverse();
 
        // Merge cluster2 into cluster1
        cluster1.push.apply(cluster1, cluster2);
        delete colorToCluster[color1];
        delete colorToCluster[color2];
        colorToCluster[cluster1[0]] = cluster1;
        colorToCluster[cluster1[cluster1.length - 1]] = cluster1;
        lastCluster = cluster1;
    }
    // By now all colors should be in one cluster
    return lastCluster;
}

I wrote the snippet below, and it does the trick, but it may not be sufficient to make a generic color-sorting function. It also needs cleaning up.