There goes that theory...

...straight down the toilet! 
In my enthusiasm of a few days ago, I was absolutely convinced that the Bougainvillea I'd posted had monochromatic yellowy-orange leaves all over, with just a single small branch of monochromatic red leaves; and further, that there were no leaves transitioning from red to yellow, or vice-versa.
Explored the plant again this morning, only this time a little more closely. After a few minor bumps and scratches, suddenly, there it was: a single leaf coloured yellow on one side and red on the other, with the slightly wobbly dividing line running pretty much up the centre.
Remain convinced there's no colour transitioning going on here - that part of the theory is still standing up - but there's no doubt the monochromatic side of the theory is now looking a little shaky, to say the least.
Spurred on by this find, I really went to town on the leaves surrounding the red-leaved branch, to see if I could find any more dual-coloured examples. This can be quite an uncomfortable task when you're  trying to avoid those nasty spikes at the same time. While perched high up on a none-too-stable ladder. Armed with a decent-sized camera and lens. Mounted on a tripod.
Not a single additional half-red-half-yellow leaf to be found - which was rather comforting - but I did manage to track down a single yellow leaf that looks like it had been splotched with a large drop of red ink. (See today's Extra photo.)  Which wasn't so comforting - and in fact, was a little unsettling.
Then again, that's only 2 dual-coloured leaves in amongst several hundred in the immediate area, and several thousand over the whole plant. So they might well be the exception that makes the single-coloured rule. As if they'd accidentally bumped into a bit of random red pigment in the early stages of their growth cycle.
On the other hand...nah, had enough of theorising for one day. It is what it is seems to be the best way - and certainly the easiest - to reconcile these botanical anomalies, without the need for any nuanced deductive reasoning or post-hoc rationalisation. That stuff can hurt your head, and distract you from smelling the roses.