Spats aren't bad; I've got a pair of WWII leggings that I wear sometimes. It seems that in picking out footwear the two important factors are color and shape. For color, finding something complementary is not too hard, and if you have trouble you can stick to just dark brown or black. For shape, you have to concentrate on what has been called visual balance. A hiking boot that reaches just past your ankle and kilt hose pulled up to your knee can be visually awkward; it breaks up your sight. But spats seem to work ok. Why? because they are fit snug to your leg and keep the look streamlined, whereas hiking boots are usually bulky.
A little "off-topic" here, but I just wanted to clarify that "spats" and leggings" are not the same thing, although they do serve similar purposes. Spats are more for "dressy" attire to protect the shoe from wet conditions, mud, etc. -- hence their name, "spatterdashes". Leggings are longer, usually right below the knee, and are usually seen as part of military-issue uniform or for outdoor events, such as hiking.

I have a pair of reproduction US Army Issue Model 1894 Leggings I wear for Spanish-American War reenacting, and I quite like them -- not only do they look "natty", but they are also quite practical in keeping dirt, grass, rocks, critters, etc. out of your shoes -- and it's not too hard to put them on. But they must be worn TIGHT -- almost cutting off circulation.

There is a lot of evidence that Scottish Regiments serving in North America during the Seven Year's (French & Indian) War wore Native Leggings made of wool with beaded ties, as the French were doing. Again, very practical considering the dense forest that these campaigns took place in. In the First World War, the US Army abandoned the canvas legging for the British puttee, or leg-wrap, which was more practical for the damp conditions of the trenches,only to "re-adopt" them again in the Second World War until 1943-44.

Leggings are still around today, for skiing and other winter activities, and the Swiss & Norwegian armies still issue them as "kit". We still see them in the US as part of dress uniforms for colour guards (The US Navy comes to mind).

Sorry, reverting back to "reenactor mindset" there...

Cheers,

T.