Early spring I planted a Iceland Poppy. It had bright orange flowers when I planted it. Due to transplanting, all the flowers died off. It's starting to grow a lot of new flower buds now and some have opened. But now the flowers are yellow. This happened to me a few years ago with lupine. I planted red, the next year they came back a dark blue. Why would the color change. Especially in a short time like the poppies did.

This thread moved to Perennials forum, where hopefully you should get the answers you seek.

As for the Lupine it is possible it reseeded and when they do usually revert to either purple or white not coming true from seed. How long have the now poppy flowers been open, it might be that they open yellow and mature to orange. Some Echinacea do that. Or was there more then one plant in the pot since they come in both colors. Hopefully someone who grows them will see this.

Re the horticultural Icelandic poppies: In addition: perhaps the expression of the genes for flower colour are affected by environmental growing conditions. Hence, perhaps some aspects of the growing conditions changed.

More flowers opened on this plant, now I have some white and yellow flowers. I did some looking and multiple colors on the poppies is more typical then one single color. Growing conditions in a green house from where I bought it may have contributed to the single color of orange. I like the multiple colors better anyway. it just amazed me to see the color change. Thanks for all your help

Wikipedia below:
In the wild, the species flowers white or yellow (white dominant). Other flower colours, obtained by cultivation, are recessive to both of these. With some perennial cultivars, you do sometimes see them reverting, in part, to the wild type.
https://en.wikipedia.org/wiki/...

Still this really sounds like an environmental effect on the development of the flowers. Great suggestion about the potential role of being raised in a commercial greenhouse, Eric.