As someone who copes with constant anxiety and intermittant bouts of depression (both brought on by chronic physical health issues), I know it is easy to get caught up in darkness until it seems all color drains away from vision. I combat these feelings two very different ways in my journals:
1) I use a monochromatic color scheme (red, black, white, cream, silver and/or gold) and simple techniques to get my brain moving, sifting through negative emotions until I can cast aside worries in a dance of line and paint. I allow a lot of white space to dominate, giving me room to breathe, stretch, and regroup.
2) Alternately, I soak my world in color to act as a cheery counterbalance to internal struggles. I use complex, layered backgrounds as a meditative process; with each layer I add to the page or canvas, I peel away a little bit of what weighs down my heart. I use a lot of inspiring quotes and affirmational self-talk on my journal pages to help me express myself when I am at a loss for words.
Whether shrouded in black and white or drenched in color, I rarely write directly in my journals about my troubles. (I used to many years ago but I seemed to have worked that phase out of my system.) Currently, I either rely on the page-making process itself as a form of healing meditation or create characters that serve as stand-ins for things I am feeling and experiencing.