With digital cameras - especially ones with CCD sensors and not CMOS (which is the dominant technology these days) color in a long exposure becomes over saturated. These older cameras required enormous amounts of energy to hold a shutter open for this long and as a result you'd often get odd artifacts from fluctuations in the amount of power going to the sensor.
With film you have a whole different issue called reciprocity failure. It has to do with the rate of exposure not being constant but on a gradual curve. Meaning a long exposure that should be properly expose at 40 seconds - depending on the film stock - might actually require 45 seconds. The further you stretch the exposure - the further the distance between the stock's absolute exposure value and reciprocity failure value grow. Reciprocity failure can result in some really bizarre color artifacts and exposure anomalies. The reason I mention this is because the odd color splotches in this photo are similar to what you'd see with film that experienced reciprocity failure exposure issues.
Cross processing - taking slide film and then developing it in a negative process - instead of a reversal process - can also create these surreal color anomalies. Fuji stock is great for cross processing. You get all kinds of odd colors and exposures out of it.