I keep white on white. If I have a 50% off Joann's coupon I buy a whole bolt at a time.

Jackie

I keep white but also keep black. I keep solid black plus black batik. They are my mainstays. I also have a tub with off-whites.

I have recently refolded all of my fabrics. I have determined that I am sorely lacking whites, off whites, blacks and greys. I have tons of greens and blues, and the pinks/purples aren't too bad either.

So to answer the question, I guess I don't really have any one thing that I must have on hand. I guess that comes from buying for the project for so many years. I don't just work from the stash...

I like to keep neutral TOTs I use them a lot for backgrounds. Have everything from WOW to dark tans

Maryv

I try to keep lots of WOW and beige/cream TOT on hand. And, I make sure I buy more whenever I go to Lancaster. Scrappy is my middle name, and I even like the backgrounds to be scrappy!

Teresa

I have a need to keep black on hand as well as WOW or creams. My stash is such a jumble that it is difficult to pick any one color that dominates but I like lots of greens available.

I keep Kona black and white and blenders is a variety of colors. I love to use blenders instead of solids with other fabrics because it adds some movement, but still reads neutral. I gotta have my Kona white and black as my basic solids.

beverly

Unbleached muslin or osnaberg in a heavier weight and they sure as hey don't make that like they used to.

I have been making a lot of baby quilts this year. I have a lot of go-with-anything baby fabrics and keep watching for more.
One I have is an allover print of small, brightly -colored circles. Another is a multicolored small stripe and a third is a print of baby objects(rattles, teddies etc.). I have lots of yardage of these fabrics. Because they are allover prints in bright colors I use them as backgrounds for baby quilts. I always keep an eye out for more of these types of fabrics.

I also have lots of whites and blacks. I keep mottled fabrics in various colors on hand to use as blenders.

~Geraldine

I like to keep white and off white fabric on hand for background. I usually have to buy more if I am making a large quilt because I never seem to have quite enough.
Linda OH

Kona black, Kona snow, and lots of WOW. For the past few years I've been stuck on WOW backgrounds and almost never use beige. I don't dislike beige but everything looks better with white or the slightly, slightly off-white of the Kona snow.

Kona solids is so modern - you are progressive Sharon!

I start to panic when I run low on Kona very black.
I also like to keep Kona white on hand - I was using some Kona from Joann's that I label 'Fake Kona', but I doubt that I will buy it anymore. I would like never to buy fabric there anymore - that's my goal!
I have decided I really like Andover dimples - wish I could buy every color. I bought a bolt of the white.

I need a better WOW or some Kona Snow; I have a paisley WOW which I love the print, but not crazy about the quality...from Joann's. Nice blacks I have and recently picked up a Moda gray as my new neutral, I find colors seem to pop off of soft gray. I'm also a fan of a neutral batik that I picked up recently.
V.

Kona Snow is the only thing I have bought as a whole bolt, so I guess that's my only must have.

I seem to use a lot of solid black for piping on quilts, and TOT neutrals for backgrounds. I like the TOT better than solids... gives it a little more softness.

I try to buy large yardages (5+) when I see them at thrift stores to have for backings. This means that my backings can be kind of interesting! I came across two pieces last week, but did not buy them because they did not appeal to me for quilt tops, and after I got home, I kicked myself because they would have worked for backings. I have to keep reminding myself that 5+ yds is not easy to come by, so if it is not awful - buy it for a backing.
Karlene