A week ago I made some fondant flowers using Wilton Fondant and Wilton violet paste coloring.

Now when I look at them some of the petals are blue instead of purple. The smaller flowers are all blue. What could have caused this? I really needed them to be violet.

It has to do with the light affecting the red colour used to create the purple colour. Items made or decorated with purple coloured fondant/gumpaste etc. should be protected from uv light to minimize the fading. Here is a link to an article about this topic. http://ericaobrien.com/blog/2011/08/on-purple-fondant.html
You could also try airbrushing or painting your flowers purple to try and save them.

Purple will fade eventually...I've had purple gumpaste fade to blue in about three hours.

Mallorymaid is right about airbrushing or dusting. If I have to do purple I either do that or use Crystal Colors to color the gumpaste, since that doesn't fade. Some brands of colors fade faster than others, too.

IT's the wilton brand for sure..it happened to me several times until I got rid of all of my wilton colors(my black turned into a nasty dark, dark green over time, and pink turned into purple) and went with americolor..never again had a problem..the light could be the problem too, ,but I did this in different lighting and STILL had the problem..

Sugarflair GRAPE ..... OR add the bicarb to your paste as in the link above