I think this is false, brown color should be the result of 2 genes cl and y+.
y+ is dominant to y and on its own produces red pods where as yy would result in yellow pods.
On top of this background the cl gene is recessive to W, where only clcl produces brown pods. Therefore a true breeding brown plant must be y+y+clcl.
In the most likely case it would have been crossed with a red pod plant, which should have the wild type gene at the cl locus so it would be y+y+WW
In this case all offspring should be y+y+Wcl, which are all red pod plants that are carriers for the brown gene.
If your curious, you could self the plant and see if it gives you 25% brown pod offspring, but it might just be less work to get someone to send you new seed stock
