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. 

As we know red corresponds to digit $2$ and green corresponds to digit $\mathrm{ }5$ , new resistance will be $500\mathrm{ }\mathrm{\Omega }$