2D is the one opening that could be just about anything sensibly. Maybe a strong option. Maybe three-suited. Maybe Flannery, or Reverse Flannery. Maybe minors.
What the hey! How about another idea?
I at one time thought about solving the high-reverse problem by having 2M show that major and clubs, with 2D as the spade-diamond hand. all light openings. This way, for example, 1S-P-2D-P-??? Not a problem with clubs. If you have enough for a high reverse, bid 3C. If not, you would have opened 2S.
Well, people like weak twos a lot. But, people seem willing to give up 2D as a weak opening, often trying this and that along the way. Seat sometimes matters.
I still think this high-reverse solving idea has a lot of merit for fourth-seat openings, but maybe 2D as spades (5+) and diamonds (4+), not enough for a weak two, is the most critical of the three. And, perhaps the most likely to be accepted.
Why, you ask?
Consider 1S-P-2H-P-3D. This is the death sequence. No 4SF available below 3NT. No room for diddly-squat. Decide, and decide now.
So, maybe you like this idea. Maybe just red on white. Maybe just in fourth seat. Whatever.