Colour band $A$ and $B$ indicate the first two significant figures of resistance in "ohm" , while the $C$ band gives the decimal multiplier i.e., the number of zeros that follows the two significant figures $A$ and $B$.

The last band $D$ indicates the tolerance in percentage about the indicate value or in another ward it represents the percentage accuracy of the indicated value. 

According to given color-coding, the values of colors are

Green $\to 5,$ Black $\to 0$ Red $\to {10}^2$ Silver $\to 10\%$ tolerance 

so, resistance is $R =50\times {10}^2\pm 10\%$

The maximum current is 

$I^{2}R=P$

$I^2=\frac{2}{50\times {10}^2}=4\times {10}^{-\mathrm{4 }}\mathrm{A}$

$I=2\times {10}^{-2}\mathrm{A}=20\mathrm{m}\mathrm{A}$