Yeah, I thought about light grey. Most of the trousers I wear casually are white, khaki, stone or grey with the occasional "big plaid" thrown in, most of which would probably look washed out when paired with a grey jacket, but I'm prepared to be convinced. I've started moving away from jeans, especially in the summer, as I'm not too fond of swap butt, which further limits the utility of light gray.
If I was to go for a light grey jacket, I would probably just get a full suit made.
I was planning on getting a lightish grey jacket myself, but not necessarily just for summer.. Maybe tan / light brown will be nice for the colour trousers that you wear?
I think texture / pattern is the key with sports jackets