Nobody wants to accept summer is over, including my new client who emailed me to ask "Do I have to give up my bright summer colors in October?" You sure don't. A summer stand alone like a light weight linen collared shirt in sea blue, orange, or mint transitions perfectly into an accent piece layered underneath a darker color or neutral tone.
If you don't already have them in your collection, get a couple of earth toned thin knits. A crewneck, v-neck or zip-up in brown, forest green, or cream will look great layered over a bright color. One caveat, summer short sleeve button downs can tend to have a looser fit. If the sweater is too snug and the undershirt too loose you'll risk resembling an improperly stuffed sausage. Avoid bumps and lumps in all the wrong places by making sure the shirt you are wearing underneath the knit fits closely to your body.