You can just change the colors in the "sch=" part.
"http://www.speedsolving.com/wiki/extensions/algdb/vcube/visualcube.php?fmt=png&bg=t&size=200&pzl=3&sch=wnnnnn&view=plan&case="
or
"http://www.speedsolving.com/wiki/extensions/algdb/vcube/visualcube.php?fmt=png&bg=t&size=200&pzl=3&sch=wddddd&view=plan&case="
Replace the w after sch with y for yellow etc. You can add "cc=w" or whatever color for more contrast as well
"http://www.speedsolving.com/wiki/extensions/algdb/vcube/visualcube.php?fmt=png&bg=t&size=200&pzl=3&sch=wnnnnn&cc=w&view=plan&case="
or
"http://www.speedsolving.com/wiki/extensions/algdb/vcube/visualcube.php?fmt=png&bg=t&size=200&pzl=3&sch=wnnnnn&cc=d&view=plan&case="
As for the numbers, just use an image editing program to put them on. I don't think visual cube can do that part.
"http://www.speedsolving.com/wiki/extensions/algdb/vcube/visualcube.php?fmt=png&bg=t&size=200&pzl=3&sch=wnnnnn&view=plan&case="
or
"http://www.speedsolving.com/wiki/extensions/algdb/vcube/visualcube.php?fmt=png&bg=t&size=200&pzl=3&sch=wddddd&view=plan&case="
Replace the w after sch with y for yellow etc. You can add "cc=w" or whatever color for more contrast as well
"http://www.speedsolving.com/wiki/extensions/algdb/vcube/visualcube.php?fmt=png&bg=t&size=200&pzl=3&sch=wnnnnn&cc=w&view=plan&case="
or
"http://www.speedsolving.com/wiki/extensions/algdb/vcube/visualcube.php?fmt=png&bg=t&size=200&pzl=3&sch=wnnnnn&cc=d&view=plan&case="
As for the numbers, just use an image editing program to put them on. I don't think visual cube can do that part.