In that case - I haven't come across any , but using gray Harrisdetectors can be used and applied to RGB images because all it gives are the coordinates and you can extract them.
You can use the bjilt-in wavelet toolbox in Matlab to perform multiresolution analysis: https://www.mathworks.com/products/wavelet.html
Also you can perform a multiscale analysis and segmentation using fractals. A matlab code using the box counting algorithm can be downloaded from: http://www.mathworks.com/matlabcentral/fileexchange/44951-fractal-dimension?focused=3807574&tab=function