I've never done a night painting in pastel, so I thought I'd give it a try.  Unlike oil painting at night, you don't have the color mixing issue.  (In the glow of my headlamp, Ultramarine Blue oil paint looks a lot like Alizarin Crimson oil paint, and it's mostly because I always arrange my palette in the same way that I can tell them apart.)  But you do have the color selection issue -- which is, in my mind, almost as difficult.
We had a beautiful full moon this morning, and when I woke around 4, I decided to take advantage of it.  I loaded up my pastel gear and hiked down to our beach through the apple trees. The ripe apples seem even more fragrant in the night.  As I moved out into a clearing, I saw Friar's Head, lying in the distance like a black slab in a silvery sea.
I set up my pastel box.  I keep it well-organized.  It has six sections, one for each color family.  I divide each section with cool colors at one end and warm colors at the other.  In addition, I sort the pastels in each section by value.  (See the photo below.)  With this level of organization, you'd think it'd be a piece of cake in the dark to find the correct cool, dark purple I need.  Not so - there are subtle but important variations among those cool, dark purples.  They were almost impossible to see under my headlamp.
I found myself looking at the scene, deciding (or guessing) what color a certain shape before me was, and then reaching into the box where I remembered that particular color should be.  But was it the correct cool, dark purple?  The best I could do was get right the color family, the temperature and the value.  Whether it was a slightly redder purple or a slightly bluer one was hard to tell.  But this isn't a problem unique to pastel; it's the same with mixing oil paint in the dark.
Unlike oil paint, however, which stays on the palette where you put it, pastel sticks don't.  I have a little tray (my "working palette") that I put my pastel sticks in as I work so I can find them again easily.  Well, they rolled around and got jumbled up a bit.  Oops!  Is this the purple or the green?  I had to work very hard at keeping the pastel sticks that were in use separate.
I ended up focussing more on value than anything and tried to approximate the temperatures.  Even so, I was pretty satisfied with the result.  Here's the painting after a few minor tweaks in the studio:
"Friar's Head, Moonlight"
5x7, pastel, en plein air - SOLD

