More likely it's due to the weather temps and/or the amount of sunlight it's getting. Mine is a different shade each time it blooms from a bright orange to almost cocoa colored.

I'm not sure what effects pH or any nutrient issues may have, but Seil is right. Cooler, damper temps encourage Hot Cocoa (and all the other 'brown roses') to provide the russet tones. Brown Velvet, even in brilliant sun, provided the chocolate velvet petals as long as it was cool to cold. Ramp up the heat and the color quickly shifted to bright orange. Leonidas does similarly as do Jocelyn, Edith Holden, Iris Web (more taupe than orange), Black Tea, Brown Study and Victoriana. As long as you're feeding it a properly balanced fertilizer and the rest of the plant appears normal, just wait until your temps cool off and you should see the desired coloring reappear. You COULD try cutting a flower just beginning to open with a short stem, then put the whole vase in an enclosed plastic bag in your refrigerator (frost free units dry out the flowers) and try opening it where it's cool to see how the pigments respond to temperature. It worked well with the others listed above. Kim

I agree with Seil and Kim. Try moving it to partial shade while its dorment. Mine is in the shade of a weeping willow, so it only gets dappled sun and stays a nice russet/brick color. :)

Tammy

Thanks, everyone. I'll either try moving it out of full sun or learn to love the seasonal variation.

Or stretch a shade cloth canopy over it during the summer. Mine would revert to that beautiful color and double the petal count in any overcast conditions, in lots of sun it was a rather ordinary orange-red semi-double.

Feh! Mine has died (and you have to be a bit negligent to see off a rose in the UK and this is my second one this year).