With grey I prefer green, but red works too.
Prefer red with navy. Red polka dot tie under a navy chalkstripe is a powerful look IMO.
I've a red cashmere shawl collar cardigan and a red sea island polo sweater, both from the dearly departed Sulka. And a cashmere scarf, silk knit tie, socks and silk knots. That's about it, unless athletic wear is included.