what enviromental factors effect the color (shade) of a flower?

Answer 1

Soil will affect the colors of some - I know hydrangeas can be either pink or blue by the pH of the soil they grow in because we had these around our house when I was a kid.

I know white trilliums turn pink as they get older, but I don't know if you consider age an environmental factor.

This link says temperature intensifies colors: http://ag.arizona.edu/pubs/garden/mg/indoor/environmental.html

This says it's light for alfalfa flowers: http://www.naaic.org/Resources/colorguide/flowercolor.html#Intensity

Answer 2

Plant stress, such as from drought, insect attack, or plant nutrition (too much or little) can cause different levels of pigments in flowers, and as a result, different colors.
Iris are prone to producing white flowers if stressed when moved. Sometimes the original flower color will return, sometimes the plants will bloom another color.
Mutations or sports appear in both flower and leaf color. These produce the wide range of variegated leaves and new colors in classic varieties. Camellias may undergo a spontaneous mutation and have different colored flowers or a patterned flower right next to the old ones.

Age effects color. Tulip flowers tend to turn yellow or white as the bulbs get older. Gladioli tend to turn yellow. This is why many growers discard older bulbs of some types.

Pigments in roses are UV sensitive especially yellow pigments. Some red roses change color when exposed to the sun, they 'blue' because some of their pigmenting, containing yellow, bleached out leaving a bluer appearance. Strong colors in complex combinations show the greatest variability as tiny changes in one of the rose's pigments can shift the perceived color quite a bit. Roses with pink, cerise, rose, or crimson tend to be the most stable.

Another impact can come from the soil. Certain minerals will affect color shifts if they are not present. Acidic soil with aluminum turns hydrangeas blue, more alkaline soil with iron produces pink flowers.

Some people claim alfalfa pellets or epsom salts have helped roses achieve stronger colors but I do not know how they measured this or if it was just what they perceived.

UV will turn white roses pink in spots as the rose ages.
Cooler or hotter temperatures can also cause changes in the pigments the plant produces. Roses are capable of having both carotenoids (yellows) and anthocyanins as flower pigments. If the rose expressed more yellow usually but actually had a very low (unnoticeable to the human eye) concentration of anthocyanins it might show temperature related color shifts. Such a cultivar might bloom yellow with a blush/overlay of red making them appear peach toned when they opened on cool days in early spring and then become pure yellow as the temperature increased during the day or as the sunlight became more intense in summer.

Roses are so noted for their response to UV that they have been bred for their phototropic color shifts.
Some roses producing staged color shifts include Joseph Coat, Mutabilis, Masquerade, Double Delight, or Flutterby that begin yellow and shift to cerise tones.

http://www.mooseyscountrygarden.com/rose-garden/masquerade-climbing-rose.html
http://forums2.gardenweb.com/forums/load/roses/msg0214105220783.html?23=
http://forums2.gardenweb.com/forums/load/rosesant/msg0914474811269.html?6
Plants without the yellow just go trough the pink to red shift like 'Archduke Charles', ‘Orange Smith’,
http://members.aol.com/srbrubaker/roses/rcolor.htm
http://rosefile.com/RosePages/ColorsOfTheRose.html
http://forums.gardenweb.com/forums/load/botany/msg0611230230825.html
Inheritance of Color
http://www.rdrop.com/~paul/legrice2.html

Some flowers change color to indicate they are pollinated. These include lungworts (Pulmonaria), forget-me-nots (Myosotis), or other members of the Borage family plus hellebores and larkspur.

Answer 3

Colour of flower used to appeal to preferred pollinator.

Pollinator could be insect (bee, fly etc), bird or animal.

Colour depends on pollinators vision characteristics and other factors.