Tom,
I guess that I am a little late to add my two pence worth - John Mac has given you a great listing for bead sizes.
For colours, think in terms of gold for coloured water, copper and brown for when the water is clearer and gold might be a little too flashy - and you can never go wrong with black.
For PTNs with added attraction, consider a coloured bead in the thorax area -orange, pink, green - all will work and or course pink is a must use colour for Grayling.
The following website will give you details as to which beads fit which hook sizes:
http://www.flytyingboutique.com/stor...=35&category=2
The Dohiku hooks are really strong and with a long spear, offer great hooking.
If you are concerned as to sizes, let me know which you are interested in and I can take some photos of those hooks against a ruler for you.
Kind regards