I don't dislike UGGs. They can look very nice. But I'm sure even the best pair of UGGs will look silly worn with black leggings.
The ultimate tan UGGs look is the way shown in many of their advertisements. Stick to similar colours; white, cream, beige, camel, and perhaps soft browns, blues or greys. Wear them with a dress, shorts or a skirt and bare legs...that's the only way to look hot in UGGs.
There's one problem with this however, it's very impractical. If its warm enough to wear short floaty linen dresses or very short shorts, then you're not going to want your feet covered in fur are you? The choice is a) summer weather and very sweaty feet or b) cold legs and cosy feet...except...wait a minute...if it snows or rains you're screwed (So basically, every day you wear UGGs in Britain you take a big risk). This is OK because fashion doesn't care much for practicality, we suffer for our style; yet there seems to be this myth that UGGs are practical fashion. UGGS are so popular because most people would love to go everywhere in their slippers, and would do so every day if they felt they could still look fashionable, or even just look sane. The worst part is that people believe the UGG is so fashionable that you can wear it with absolutely anything and still look super cool, therefore ignoring one simple rule - your shoes should match (or at least compliment) your outfit.
Black leggings are also loved for being both comfortable and fashionable, another 'wear it with anything' item. The difference? With black leggings this is mostly true. They ARE comfortable, they ARE practical, and they ARE...sort of...fashionable. They solve those 'is it a dress or a top?' issues perfectly, and they allow an active girl to wear a dress or skirt without worrying others will get a glimpse of their knickers. Generally, in the real world away from high fashion, leggings are a dignified, acceptable fashion item that it's hard to go wrong with.
Hard to go wrong, that is, unless you own tan UGG boots.
With jeans? Fine
Bare legs? Yes
Black Leggings? - No. Just NO.
Think about it - would you wear black trousers with brown shoes?