If you are planning to cook them whole, it is better not to peel them to prevent them from losing their color. (consumerhealthdigest.com)
A unique fantasy world in which lost colors hold the key to salvation.... (kindlenationdaily.com)
If not serving immediately, this can stay in a warm oven for some time, but be careful that the green beans do not lose their color and texture! (bostonmamas.com)