Your colour head modification sounds great ! And it may work very well for you.
However, once you are printing you should compare with the original Leitz enlarger head. I am quite sure the whole light system contributes to the character of prints made with the 1c and the Valoy II.
Leitz USA (or Canada) made a beautiful under-the-lens filter holder, but it is hard to find. I attach a picture of this holder.
I have modified Beseler 23 filter holders for this purpose, takes 15 minutes. See picture . . .
I use the 1c with the filter tray and I use the older 1c with this filter holder under the lens. Providing your filters are clean and undamaged, there's no difference.