Sometimes when I’m writing in the Skritter iOS app, as I draw the stroke there is a blue tint in the black line. Kind of like an etching effect.
It’s hard to describe and I can’t screenshot it (the effect ends once the stroke is written).
Has anybody else seen this behaviour? Any idea what causes this?
Looking at it, I think if you get a few right in a row, you start to get this effect. The “ink” starts out black when you haven’t got any right. As you get more right, it becomes blue, but still “dries out” to a black colour. You also get a blue halo effect around the “pen nib”, i.e. your finger. I think there’s maybe a light dot in the middle but it’s obscured by my finger as I write.
And in the dark theme (not available on iPad), you start to shoot sparks as your hot streak heats up.
Thank you both for the replies! I’m pretty devastated that I can’t shoot sparks now though 
If you zoom around making a continuous line on the iPad, it will “explode” when the line gets too long. Not quite sparks, but fun.