Green spans a huge range and the same nominal shade shifts with fabric type, lighting and washing. Two garments can match on arrival and drift apart within a season.

Either let one garment carry the colour, or pick clearly contrasting greens. Near-identical shades read as a mistake; obvious contrast reads as intentional.

Only if the motif is subtle enough to read as pattern rather than as a date. Otherwise accept that this is a single-occasion purchase and spend accordingly.

An openable outer layer over a printed shirt. The day usually involves an outdoor parade then hours indoors, so repeated temperature changes matter more than one steady condition.

Usually not. It is still cold in most places and parade routes are exposed. People underdress for this date because the calendar says spring.

Yes. Group orders are the norm for this date. Stadium giveaways covers ordering across a spread of sizes with a firm deadline.

Yes. Printed flags and other display pieces work for venues and gatherings where you are not dressing people.