import re
rx = r"(?<!:)\b\w+:\w+\?"
s = "\"I want to find JKD:Jdj:SL? and YK:kd? JKD:askdlfj:Jdj:SL? jklj? jklj:jklj\" "
print(re.findall(rx, s))
aW1wb3J0IHJlCnJ4ID0gciIoPzwhOilcYlx3KzpcdytcPyIKcyA9ICJcIkkgd2FudCB0byBmaW5kIEpLRDpKZGo6U0w/IGFuZCBZSzprZD8gSktEOmFza2RsZmo6SmRqOlNMPyBqa2xqPyBqa2xqOmprbGpcIiAiCnByaW50KHJlLmZpbmRhbGwocngsIHMpKQ==