Ok, the difference in the crests is just artistic lisence. They are depicting the exact same thing, just drawn slightly different, which is perfectly legitimage.

The different tartans are because Ogilvie, like many other clans, has more than one tartan.

The one they are most well known for is Ogilvie of Airlie, which is famous as being the most complex tartan with something like 72 color changes in one repeat of the pattern. Now, with a tartan this large, you need a very big peice to see the whole pattern. Most swatches of the tartan you see are relatively small -- same thing with images on the computer. So if the picture you are looking at only shows part of the pattern, then another picture or swatch shows a different part of the pattern, it can look like you are actually seeing two different tartans.

The Ogilvie tartan you'll most often worn is Ogilvie of Inverurie (sp?) aka Ogilvie Hunting, which is a more usual green adn blue design.

There are other Oglive tartans in addition to these two, many of which look like simplified versions of the Ogilvie of Airlie tartan.

(Personal note, I have a great-grandmother whose maiden name was Storey, which is a sept of the Ogilvie clan. Every now and then I toy with the idea of making a kilt in the Oglivie of Airlie tartan -- just because I can -- but you only seem to ever find it in the ancient colors. And all that orange and light blue just doesn't do it for me. I've seen it in a kilt a couple of times in the modern colors and it looks much better.)

(Another side note -- Oglivie of Airlie is the same tartan as Drummond of Strathallan. Come to think of it, Drummond of Perth is the same as the Perthshire district tartan, and regular clan Drummond is the same as the Grant tartan. Those poor Drummonds with not tartan of their own!)

Aye,
Matt