Answer
$\lambda = 668~nm$
Work Step by Step
We can find the radial velocity of the galaxy relative to us:
$v = Hr$
$v = (0.0218~m/s~ly)(2.40\times 10^8~ly)$
$v = 5.232\times 10^6~m/s$
We can find the observed wavelength:
$v = \frac{\lambda-\lambda_0}{\lambda_0}~c$
$\frac{v~\lambda_0}{c} = \lambda-\lambda_0$
$\lambda = \frac{v~\lambda_0}{c} + \lambda_0$
$\lambda = \frac{(5.232\times 10^6~m/s)~(656.3~nm)}{3.0\times 10^8~m/s} + 656.3~nm$
$\lambda = 668~nm$
