TRY BEFORE YOU BUY
I am an avid buyer of cosmetics on eBay, and although you may view a basic guide of various shades of foundations, powders, lipsticks, eye shadows, blush, eyeliners, mascaras etc from the photographs supplied by eBay sellers, I also research the websites of the related cosmetics' companies to cross reference a product. In some cases, there has been an obvious discrepancy in the photograph submitted by the seller and that of the manufacturer. Most sellers will be happy to rephotograph an item they have on sale if you contact them and state you cannot see the shade or the picture may be too dark to judge the true colour in the photograph they have supplied. The Colour Resolution settings on your computer monitor also vary.
Therefore, if you are looking to purchase a product for the first time and there is even the slightest doubt about what might suit your skin colouring, it is ALWAYS advisable to consult a department store/pharmacy/cosmetician for the most suitable product and shading. In other words, TRY BEFORE YOU BUY then come back to eBay to bid or "buy it now"!.
Additionally, I constantly check for worldwide opinions and reviews on all cosmetic items at www.makeupalley.com. Through this forum I have discovered and purchased items on eBay that are not from major cosmetic companies and have had some excellent and unexpected results.
So when selecting shades of colours that would be unique to your own skin and hair colourings, be safe and try first. This will eliminate disharmony between seller and buyer, and the inconvenience of paying, posting, returning and refunding of unsuitable items. Also, due to hygiene reasons, if cosmetic items have been opened and tested, then foundation, lipstick, powders, mascara etc should not be resold. This is where you should rely on a seller with a good reputation or better yet, be a consciencious seller or a vigilant buyer.
Besides,when you do find your most suitable colours and shades, it will be easier to repurchase the product on eBay.