I am trying to create a factorial design in R for a conjoint analysis experiment (like SPSS orthoplan).The factors I want to use are nominal variable, for example, the color of a product can be green, yellow or red.I have tried the following code,but the result is nor balanced, nor orthogonal.

f.design <- gen.factorial(levels.design,factors="all")

In order to have a balanced solution in a design with nominal factors, I expect it should at least be :

nTrials=prod(unique(levels.design))

There's a package anyway that could deal with such an issue, it is the package FrF2 by Prof. Ulrike Groemping, but it handles only dichotomous variables and I cannot figure out how to use it to solve my problem. Any suggestion would be appreciated!