Forum Flora Germanica

Local guy says Clavariadelphus pistillaris, but has no description of color change for pistillaris, has mild to none description of color change for ligula, namely red.
Yelow specimen also changes color but much much less. I guess we could imagine red at bruises.

Clavariadelphus helveticus?

Croatian page also says meat becomes dark on air for https://www.cromushrooms.eu/594-fungi/b ... istillaris

In my region I can only find C. pistillaris, taste slightly bitter, flesh yellow with KOH, not getting a dark red-brown colour inside. (Matching descriptions afaik).