@bgruis:
German breweries do not use wheat malt in Kolsch. Most of commercial examples is 100% pilsner, some with ~5% vienna or light munich. Hop aroma low to none, so it's better to add hops @60' and then @20' before end of boil. And ofc only German noble hops (Perle is not a noble hop, very dominating, can cover all other hop aromas even if added @20').
@TheBeerist:
Helles is much more malty in flavor & aroma, kolsch should be crisp and dry, more in line of dortmunder. As the grain bill is not noticeably different, the thing that makes difference is yeast - southern german strains accentuate malt, while other german strains are more balanced. And bitterness - helles is low, pils is high, dortmunder is in between.