admin amount available avoid cart color colors combination combinations configure control create describe edit enable feature format green happened individual inventory item lines list medium named next note offer options ounces particular price product red screen seller selling setting size standard stock units variants wanted weight wish

Is there anyway for me to list an item that is available in a size small in 3 different colors, but in a size medium in 4 colors?

Certainly, you can configure your product using our Variants feature:
http://www.e-junkie.com/ej/help.variants.php

In the case you describe, you would only create variant-configuration lines for the particular color-size combinations you actually have for that product.

When you Add or Edit the product in Seller Admin and enable the "Variants having individual price/weight/stock/SKU" setting for that product, on the next screen you can name up to three Options (you will specify only two, named Size and Color), then below that provide a list of every possible combination you will offer, following our standard format of:
SKU,Price,Ounces,Stock,Option1Value,Option2Value,Option3Value

E.g.:
Widget-SmRed,12.95,11.0,25,Small,Red,
Widget-SmGrn,12.95,11.0,23,Small,Green,
Widget-SmBlu,12.95,11.0,31,Small,Blue,
Widget-MdRed,12.95,11.0,25,Medium,Red,
Widget-MdGrn,12.95,11.0,14,Medium,Green,
Widget-MdBlu,12.95,11.0,19,Medium,Blue,
Widget-MdYel,12.95,11.0,8,Medium,Yellow,

(Note here I happened to give every combination the same price and weight, but you can make them different if you wish, and I gave each one a different amount of in-stock inventory units, if you wanted to enable Inventory Control in the cart to avoid selling a sold-out combination. :^)