Minimum Requirement: Qubicle Basic Edition
You can easily create a gradient between two colors in the Swatches Bar. The number of swatches in the middle determines the number of gradations between the two tones.
Select the first swatch. Here, the red on the top left side is selected as the starting point of the gradient.
Holding down Shift, select the second swatch. The blue on the top right side is selected as the end point of the gradient.
Select Swatches > Create Gradient. There is now a smooth transition between the two colors.