There's no need to worry. Virtually all single mode optical recievers are wide-band (1300-1600nm) capable, so they receive any signal without caring what the wavelength is. As long as you're not exceeding the max Rx value, you'll be fine.
The 1310 Tx is typically around -3 dBm, so the Rx port of the 1538.98 XFP would typically require about 5dB of attenuation to bring it below -7 dBm.
The 1538.98 Tx is probably around +1, so the Rx port of the 1310 SFP+ might need a little attenuation, but you're probably OK as is.
