Harmonic Balancing

I rememeber reading somewhere that the crank shaft pullys are harmonicaly balanced... im wondering if this is true and to what impact painting the pulley may have.

none.
the pulley is harmonic damper that absorbs resonation from crank and smooths out accessory belt drive. check the bonding between the 2 parts of pulley as if becoming loose ideally need new one .

Not true really although they are obviously balanced when produced

The stock pulley will however allow for slight engine balancing irregularities which if not fitted will cause you issues holding a stable ignition timing map at certain rpm's, plus aftermarket ones (with exception of Forge) are likely to give other issues such as oil leaks etc especially around the front main oil seal.
No problem if you want to paint it but prior to doing that i would check the rubber harmonic damper as they have a tendency to split (outer pulley can seperate throwing the belts)
Also if painting it i would mask the rubber damper or wipe it off after painting it

the rpm's you see timing scatter at are the points that vibration cause worse frequencies that the standard harmonic damper dampens via the rubber ring that absorbs vibration frequencies and turns it into heat . A lot of race engines get tuned so worst frequencies fall out of rpm range or one of minimal concern . the alloy crank pulleys are pretty much all junk .
Is an OZ manufacturer that does harmonic alloy one but it bit expensive .

Ah harmonic damping
My bad, yeah the pulley is in good condition just looked a bit scabby no cracks or seperation.

Thanks guys

Sorry mrB i never saw you posted as i was writing reply

no worries bob, 2 better than 1 .