Adding noise to hyperspectral images

I have to apply various noises(Gaussian blurr, AWGN) to a hyperspectral image(available in .mat format) . G blurr is applied on the grayscale image of an rgb image with varying sigma (variance) and for for AWGN we need to vary standard deviations. My first question is that how to apply this in case of HS images as its dimension is 100x100x200 ( it's not any rgb image of mxnx3 size). For Gaussian blurr, do I need to convert the HSI image to rgb format and then grayscale format and then apply the noise? or do I convert HS image directly to grayscale image and apply noise? I'm confused. Please tell me how to do that. And how to apply AWGN to it too.( and visualizing the images ) ( Let's take indian pines image for instance)

Thanks a lot in advance.