Sports Coat suggestion.

A gray patterned jacket.

I'd stay away from grey jackets, they are very hard to pair with trousers. Grey would in fact work with these trousers, but there aren't a lot of grey jackets that don't look like orphaned suit jackets, and they wont work with grey trousers, which should make up the bulk of your trouser wardrobe.

Just about anything in blue would work with these.

A true gray sportcoat does not look like an orphaned jacket, due to patch pockets and/or special buttons (leather, silver, etc.). It also depends on the fabric or pattern. Think camelhair or silk for the fabric, houndstooth for the pattern. Those aren't suit-like.

Blue + brown? Not disastrous, but not safe. Opens the possibilty of ugliness.

No, they dont. But these are much less common. And they still have the very large problem that they go with very few trousers. Grey SCs are a much more advanced topic.

Blue + brown is totally fine. And then OP doesn't buy a SC that only goes with these (or other brown) trousers. Blue goes with just about everything short of, well, blue.

Blue + brown (jackets/trousers) works like peanut butter and jelly.

I stand firm... It depends on the blue. But when it works, it works really well.

(By the way, a gray sportcoat goes well with everything: brown, white or blue pants, even with funkier colors like green or red... Everything but gray trousers.)

 

Yep.  I have this coat and it's one of my favorites:  http://shop.nordstrom.com/s/j-p-tilford-samuelsohn-cashmere-sportcoat/3353307?origin=keywordsearch&contextualcategoryid=0&fashionColor=&resultback=0

 

^ That coat looks like an orphaned suit jacket to me.

 

And, while a gray sportcoat may work in some scenarious, it certainly doesn't "go with everything" and is not very versatile. There was a sportcoat thread recently. The guy running the thread found one picture of a decent outfit with a gray coat. He found dozens for the other colors (blue, brown, etc).

I like grey herringbone odd jackets and have one myself but am not generally a huge fan of navy odd trousers with a jacket, something I think a fair contingent of the forum agrees with. The issue of versatility comes up more when you mostly wear grey trousers and do not have many navy odd trousers. A grey jacket does not work as well there. I generally wear my grey herringbone jacket with cream colored pants and various shades of tan / brown, but I think navy goes just as well with these. Navy has the added advantage of working with grey trousers as well.

This being said, it's not clear how many odd jackets OP has. If he already has a few, then adding a grey herringbone may not be a bad idea. If he's starting out, a navy odd jacket is probably a better choice. Just my two cents.

I'd go gor a heather tweed sportcoat which come in many colors.
The advantage of heather is that it has texture but no definite
pattern. Therefore it'll go with patterned slacks such as donegal,

Some examples from OConnells:

http://www.oconnellsclothing.com/images/P/southwick-sport-coat-h-17646p.jpg

http://www.oconnellsclothing.com/images/T/southwick-sport-coat-h-17604t.jpg

http://www.bing.com/images/search?q=heather+sport+coat&id=3E278E980EC721E47C4FB687D0FE4B98FDE108FD&FORM=IQFRBA#view=detail&id=3E278E980EC721E47C4FB687D0FE4B98FDE108FD&selectedIndex=0