For this challenge I considered the different possibilities, and I think as the month progresses I'll interpret it flexibly. Selecting the colours of the spectrum with their different pastels and blends in addition gives us lots of choice. Selecting one colour and isolating it in a B&W image is another possibility. I felt somewhat tempted to follow Johnny Cash with the song he wrote about Ireland's forty shades of green but reckoned I'd turn green myself in a short while....
So here's my entry for June 1: a dash of yellow from a meadow
http://www.pbase.com/image/97931364