Just learning gumpaste flowers,books always refer to use nontoxic pastel caulks to brush on detail. What?Where? in Ontario Canada if anyone knows ??
I googled "pastel chalk canada" and came up with lots of links, including this one:
Most stationery stores or craft stores will sell them.
To add colour to gumpaste flowers, first run a sharp knife down the side of the chalk to produce a fine dust and then use a brush to apply the dust to your flower. Best to gradually build up the colour so don't load up your brush too much. Using two similar colours will give a better depth of colour.
Hope that helps,