If you only own a few jackets, you may have picked black and navy blue. These colors are versatile, and they are great for formal occasions. Light gray does not have the formality of black or navy blue, and so it tends to be more casual, but it is still completely acceptable in a formal setting. It is a color that is neutral, so it tends to fit in anywhere. Since we a dealing with a light gray, they would be jackets that would traditionally be worn in the summer or spring, but these old fashion rules no longer have to be followed.
Here are two examples. I like the Allegra K model on the right and how it almost looks like a sweater:
Light gray sport coats pictured:
Left: Darya Trading Men’s Blazer One Button Modern Fit Coat Charcoal Gray
Right: Allegra K Mens Korean Long Sleeve Solid Color Simple Design Casual Blazer Light Gray M
If you are worried about vast contrasts in your outfit, avoid black pants and/or dark colored shirts. But remember that contrast can be good. Light grey, just like white, goes very well with black. As with jackets of any other color, you have several options when picking a jacket. Double-breasted or single, two or three buttons, narrow or wide collars, etc… Then there is the material itself. A thicker fabric will be appropriate for autumn and winter, while a thinner one can be worn all year round. When it comes to certain fabrics, the jacket may be considered casual.
Two more examples – I like the tight one on the right:
Left: Kenneth Cole Reaction Slim Fit Linen Blend Sportcoat Heather Gray
Right: Zeagoo Men’s V-Neck One Button Blazer Suit
Pictured above: 1- Salvatore Exte Men's 2 Button Suit Separate Jacket Sport Coat Blazer 2- Orvis Lightweight Highland Tweed Sport Coat / Regular 3- Michael Kors Light Gray Wool Textured Two Button New Men's Blazer 4- Gino Valentino 1 Button Jacket Windowpane Gray Blazer 5- Ralph Lauren Classic Fit Light Gray Textured Two Button Blazer Sportcoat