I used to get migraines quite frequently: about once every six or seven weeks. At the risk of tempting fate, I've not had a 'real' migraine for a few years (one of the very few positive side-effects of the anti-depressants I was on for a few weeks). I can't say that I miss them.
I once had an argument with somebody at a conference who said that they wouldn't wish a migraine on their worst enemy. I would. In fact, I think that everybody should have one migraine in their life, if only to put paid to the fiction that a migraine is "a bit of a headache." Each person's migraine is an individual nightmare. No two seem to be the same. I think most of us get the completely disorienting pain and nausea, and the agony of somebody's driving a rusty tent-pole down from the top of your head right through your palate. After that we seem to get a variety of scary experiences.
I'm slightly synaesthetic as a matter of normal course. Nothing spectacular, and certainly nothing as interesting as the reader who told the Radio Times:
"To me Thursday evening has always been pale pink with a faint green stripe growing broader towards nine o'clock. I am sure that all your readers will be thrilled to know this."
In my case I usually just have a slight blurring round the edges between sight and sound: some sharp sounds have a vague visual component, a bit like a flash of light caught in the corner of your eye or. If I'm really tired they might translate into a momentary flash of some dark amorphous shape, a bit like the negative version of the shape you see when caught unawares by a bright light. During a migraine this was amped up to the max, to the extent where some noises almost became a physical assult.
I'd know I was leading up to a biggy by the signs. At the time I was sharing an office with Jimmy Huddersfield; whenever his 'phone rang I'd get a jab in my head (at the parietal/post-orbital boundary) and a messy navy-blue rectangle would sort of hover about three feet away to the left. The idling of a bus engine was vaguely orange. When the migraine proper kicked it all I could do was lie down, close my eyes and watch the firework party, in between mopping myself down and wiping up the sweat.
These days, touch wood, I just get the preliminaries. The worst I get is the dizziness provoked by high-contrast repeat patterns at the periphery of my vision (think shopping centre designer vinyl flooring). I reckon that's bad enough.
My sympathies, for what they're worth, to any of you who suffer the real thing.