IR transmitter Frequency for Universal Remote of TV and AC
The given frequencies of 38kHz, 36kHz, 40kHz etc are carrier frequencies, and has nothing to do with the wavelength of IR LED used. Those frequencies are the rates at which IR LED is switched on and off. They are further modulated by the signal waveforms.
However, while considering the receivers, only a specific receiver works for a specific carrier frequency. For example, use TSOP-1738 for 38kHz carrier frequency. The output of the receiver will be just the signal waveform (carrier gets filtered out)

So as far a universal remote is considered, any IR LED should work.