Nylon dyes very easily, so dyeing your light blue to a dark brown should be easy. I think your results will be positive... not a vomitous bile color when done :). My ULA Ohm was a 'lightish' green, which was then dyed black, it hasn't bled through onto any clothing from rain or sweat as far as I can tell. My MLD Burn pack which was originally a gray dyneema color is now a deep navy blue, haven't used this pack since summer before it was dyed so I cannot tell how the color will hold up but I'm not worried. I didn't notice any difference to the DWR properties or hand of the fabric after dyeing both packs. The biggest thing you have to do is rinse until your sick of rinsing, after 30 minutes of rinsing you'll think you removed all spent dye from the pack... only to then rinse again and find the water tinted. I added a mild detergent to my rinse water which seemed to help remove more spent dye than water alone, also helped reveal how much unused dye was floating around in the pack materials, particularly the shoulder straps and hipbelt. As far as knowing how two different colors will look when combined, I'd recommend finding a swatch of dyneema and testing it out first before dyeing your Pinnacle, or you can do what I did and just hope for the best. Worst case scenario you just dye it a darker color if you don't like it.
- Use the liquid RIT in a bottle (easy and good results)
- Presoak your pack in hot water so it's saturated from the start and takes the dye evenly once you place it in the dye.
- Hotter the dye water the deeper the color results. (medium heat stirring constantly, don't boil it or go above 180F as it might do some funky stuff to the materials)
- Longer immersion times result in deeper/darker colors. (45min- 1hr.)