It's interesting to ponder what Shakespeare -- who wrote that "A rose by any other name would smell as sweet" -- would have written about a rose that changes color. It's a curious phenomenon that some rosebushes that gardeners have tended for years suddenly sprout a new color of rose. While the color-changing rose continues to baffle the home gardener, some logical explanations can unravel this mysterious metamorphosis.
A change in rose color can occur on a rosebush in which one rose has been grafted to the root system of another to achieve a desirable rose. If the grafted portion dies, the original hardy rootstock will take over --- and that color of rose will bloom. This is the likely explanation for the gardener who suddenly sees one new rose, or a small cluster of rose buds, of a different color appear on a bush that has been another color for years. To protect the grafted portion of a rose from dying due to extreme cold, many gardeners mulch around the grafted section before winter sets in.
Sporting is a gardening terms that refers to the spontaneous mutation of the parent plant. In this case, the gardener can either enjoy the new variation or simply replace it with the color she desires. In some cases, plants that have changed color due to sporting revert back to the parent plant's color.
Sometimes color changes can be explained by cross-pollination, or the hybridization of plants. This can occur when two plants are planted close together and cross-pollinate; the offspring of the two parent plants is a hybrid of a different color.
Intense heat and bright sunlight can fade the color of a rose bloom. Providing shade for the plant through other plantings or landscape features can alleviate this problem and restore the plant's original color. If this doesn't work, another solution is to replace the plant with a more sun-resistant variety.