I can't remember if my assailants were black or white.

Trying to do something in a dream and finding it changing so you can't is very common. It's called a frustration dream. In my fight dreams, I punch my opponents as hard as I can and it doesn't seem to faze them. As for olfactory dreams, try this one on for size...

Marina's Perfume
The woman had a scent about her,
sandalwood, musk, incense, pachouly.
She wore no perfume, it was her soul I smelled;
after love it clung to me, immune to time or water.
A reminder of the day before, the night that followed.

After days it faded, finally from my fingertips, when the last bit of her
returned to air and the disappointment of my memory.
It came back when we met and touched, as welcome
as her laugh, her smile, her voice, her eyes,
the curve of her hip, the turn of her spine, the silk in her hands.

It was always there with us, or at least with me.
But she knew not her own and I doubt that she knew mine.
Our time was short, our love grew sour,
but her scent remained long after she was gone.
The last shred of her memory to fade.

A long time passed, and then some more, until
I woke one night from a dreamless sleep,
alert, awake, eyes staring at the dark;
bedclothes dripping from my sweat,
that smell clinging to my skin.

So strong that I could not escape it,
so strong my bath would not erase it,
so strong it followed me as I raced
to another room and sat weeping in the dark,
deeply breathing in her last farewell to me.