I think red fits May pretty well
Super Mario Boards
THE END
LeftyGreenMario
Red seems more February to me as well as December
Cell
What else, Ruby and Sapphire 
Paper Mario
January- Pink/purple
February- Greenish blue
March- Orange
April- Orange/yellow
May- Blue
June and July- Purple
August- Orange
September- White/Gray
October- Black
November- Light blue
December- White and dark red
Lots of these have no meaning beyond those being the colors I remember visualizing when learning the names of the months, but some relate to holidays in those months
February- Greenish blue
March- Orange
April- Orange/yellow
May- Blue
June and July- Purple
August- Orange
September- White/Gray
October- Black
November- Light blue
December- White and dark red
Lots of these have no meaning beyond those being the colors I remember visualizing when learning the names of the months, but some relate to holidays in those months
LeftyGreenMario
Ahh so
January - Ice blue (it's a winter month, and I always visualize it as like snow in the daytime)
February - Valentine's Day. Pink is for passion, red for romance and cheesy stuff like that.
March - Well Saint Patrick's day...
April - Easter colors. Bright, pastel hues and whatnot.
May - uhhhh it's that warmer spring month
June - Yellow for the summer sun, maybe aqua cyan for the waters too!
July - Red white blue, for both having 4th of July and Bastille Day
August - Gold-yellow, a sunset to signal setting summer month
September - Uhhhh it's school and the days are cooler but not quite cool... I have not much of an immediate idea maybe a yellow-green
October - Black, orange, some purple. Halloween colors!
November - Brown, it's the colors of turkey, dying leaves, and the signal the year is ending. Dark days coming.
December - Most colorful one, but primarily red and green for the Christmas colors!
So yeah May is that month that struggles to stand out for me usually and I often say it's just April but warmer.
January - Ice blue (it's a winter month, and I always visualize it as like snow in the daytime)
February - Valentine's Day. Pink is for passion, red for romance and cheesy stuff like that.
March - Well Saint Patrick's day...
April - Easter colors. Bright, pastel hues and whatnot.
May - uhhhh it's that warmer spring month
June - Yellow for the summer sun, maybe aqua cyan for the waters too!
July - Red white blue, for both having 4th of July and Bastille Day
August - Gold-yellow, a sunset to signal setting summer month
September - Uhhhh it's school and the days are cooler but not quite cool... I have not much of an immediate idea maybe a yellow-green
October - Black, orange, some purple. Halloween colors!
November - Brown, it's the colors of turkey, dying leaves, and the signal the year is ending. Dark days coming.
December - Most colorful one, but primarily red and green for the Christmas colors!
So yeah May is that month that struggles to stand out for me usually and I often say it's just April but warmer.