Correcting lens with hologram

I researched and learned that a hologram only good for single color , other colors diffract and distort the image if we use it as a lens . But at telescope correcting , they are puting a hologram between eye and the ocular to correct the image. If hologram is good for single color , why this is not same for telescope correcting.

Best ,

Mustafa Umut Sarac

The only thing of this nature that I've heard of is the use of computer designed systems using fourier analysis which act to attenuate a star without attenuating light in the immediate vicinity. This is for planetary detection and I suspect achromatic performance is less of a priority.