I Have Had A Colostomty For About 5 Years I

I have had a colostomty for about 5 years I have had very little problem with it since we found barriers and pouches that fit. within the last few weeks the material in the pouch has been a very dark green, I have also had terrible heart burn. My primary care doctor told me to elevate my head and take Mylanta. no relief. is this normal for this dark coloring? I feel great except for the continuous heartburn. My favorite food seems to be tums since I ear plenty of them but that is the only relief I get/ I called my Ostomy surgeon and it will be about 3 months before I can see him. What do you think of the symptoms and any suggestions?