How about just using natural unstained cedar lumber which handles the weather nicely, turns greyish brown?

Do yourself a favor, read the page linked below, an then use treated lumber.

Here is a link that might be useful: Raised beds with treated lumber

Odd article, that one. He's talking (2009) about a material was was banned from sale several years before. Why didn't he discuss then/now current methods of pressure-treated lumber? Looking further, I find that he paraphrased an article from a 10-yr-old Kitchen Gardener Magazine.

The new treatments are said to be safe, but that's what the earlier PT people said, too. Lying is fine in business now, standard operating procedure. But when a newborn baby already has over 200 foreign chemicals in its body, I think that's too much, so why add a little more of everything?

Now, going back to the original question...

Krylon is basically a cheap paint that tends not to last long with wet, hot/cold temp changes; it peels and looks ugly.

Cedar used to be good, but they harvest the trees so young now that they haven't aged enough to build up the protective oils. I've used them, and they didn't last much longer than fir. BUT if you use a coating on it like people who have cedar houses, that might be a different story. If you know of someone who has a cedar-faced home that still looks new (not the grey aged look) after several years, just stop and ask them what they use. What really works and what advertising says can be two completely different things.

Epoxies may be an answer, but you'll have to do your research. The link below can get you started.

You might go to a well-known paint store that just sells paint products, like Sherwin-Williams, Benjamin Moore, Rodda Paint, Dunn-Edwards, Kelly-Moore, etc and talk to the people and see what they might advise. Be sure to tell them what you're using it for, and that you need a non-toxic product. Forget places like Home Depot and Lowes, their employees don't know diddly, but won't admit it.

Sue

Here is a link that might be useful: Delta polymers & epoxy sealers

The difference in PT lumber from before 2003 and after (when it was deemed safe for use in vegetable gardens) is the use of arsenic in the lumber. PT lumber sold today isn't supposed to contain any arsenic, and is supposedly safe for gardening. That said, I have to agree with belgianpup's point. 2003 was the heyday of Christine Whitman's EPA under the Bush administration. Regulations were freely bought and sold.

I used PT lumber this to build my beds this season, and just in case, I lined the wood with plastic sheeting. Didn't go crazy, just stapled a 1' wide strip of plastic against the wood as a barrier between the wood and soil.

If I grow any extraneous limbs, I'll let you know.

The natural wood will fade quickly. Personally, I like the look of old wood. Somehow it makes the garden look more organic.
We had a lucky 'find' of some scrap plastic - 30 mil thick. It was so hard to cut, my husband had to use his circular saw. We used scrap lumber (we live on a old farm and have plenty of that around) 2x6, 3 rectangles high. I lined just the vertical insides of the bed with the plastic to help keep moisture in.