How to mosaic sentinel 2A images

I just started to use snap for my sentinel data. Now I make all 1C level data to 2A, and resample 2,3,4,8,11 and 12 to 10m resolution with the reference to band2.
then I use envi layer stacking tool to make a file with 6 bands.

Then I use envi to make mosaic, but I dont think it’s good in color balancing.
So I want to try mosaicing in Snap, but still it looks I have some problem in open the file.
I can not open the file layer stacked in Envi, but the resample step keep every band in a single img file. So what should I do next?

Which processor are you using for the L1 to L2 transformation?
After the resampling you could do a subset (Raster/Subset/Band Subset) of your file selecting only the 6 bands of interest, so you do not have to use the layer stacking in ENVI. For mosaicing you can use Raster/Geometric Operations/Mosaicing in SNAP.