$$P(\text{weiß)}={\displaystyle \frac{1}{4}}$$

$$P(\text{zweimal weiß})={\displaystyle {\displaystyle \frac{1}{4}}\cdot {\displaystyle \frac{1}{4}}={\displaystyle \frac{1}{16}}}$$

$$P(\text{grau)}={\displaystyle \frac{2}{4}={\displaystyle \frac{1}{2}}}$$

$$P(\text{schwarz)}={\displaystyle \frac{1}{4}}$$

$$P(\text{grau und schwarz)}={\displaystyle \frac{1}{2}\cdot {\displaystyle \frac{1}{4}}+{\displaystyle \frac{1}{4}}\cdot {\displaystyle \frac{1}{2}}}$$

P$$(\text{grau und schwarz)}={\displaystyle \frac{1}{8}+{\displaystyle \frac{1}{8}}={\displaystyle \frac{2}{8}}={\displaystyle \frac{1}{4}}}$$