If an exact color isn't available, blend two pastels together to achieve the desired hue. Take care not to get dust on the mounting paper. Combination Use a dark shade of marker and cover it with a lighter shade pastel to add color to rose petals. Rub off excess paint from the dried petals with a paint brush, if needed. Transparent Oil Paints Use these as you would the alcohol markers, but you'll have to mix your own shades.
Oils are less likely to fade than markers.
Some flowers take oils well, but not others.