The best pepper jam has a ratio of sweet to hot peppers of 3 to 1; so for every three cups of ground sweet pepper, there will be one cup of ground hot pepper.
For green pepper jam, use green bells for sweet and jalapenos for hot. For red pepper jam, use red bells or ancient sweets for sweet and red or green jalapenos or espanolas (ristra chile peppers) for hot. Using Thai, tabasco, or cayenne peppers for the hot reds, since they are very hot, will throw off your balance of sweet to hot and your jam will be very hot.
For every 1-1/3 c ground sweet + hot peppers, use:
3/4 c vinegar (apple cider, or red or white wine)
1/4 tsp butter
1-1/4 c sugar
(I use 2 pounds of sweet peppers and 2/3 lb jalapenos, and usually get 4 cups of ground sweet+ hot peppers from them; so I triple the above measurements– 2-1/4 c vinegar, 3/4 tsp butter, and 3-3/4 c sugar– to get the right proportion of ingredients. 4 cups ground sweet + hot peppers makes 4 half pints of jam.)
Wash and sterilize 8-oz jelly jars, rings, and lids. Into a pot, measure ground peppers, vinegar, butter, and sugar. (The butter helps prevent foam from forming.) Bring to a full rolling boil, stirring constantly. Turn down the heat, and cook until jam thickens, stirring occasionally (this might take several hours. Test jam for thickness, by dipping out a spoonful of jam and letting it cool completely. If it is like jam when cool, then it is ready). Remove from heat and ladle into sterile jars. Wipe rims, screw on lids, and process in a boiling water bath 10 minutes. Remove to a towel and let cool. Test seals and store, or refrigerate.