looking for a cheapo 2-iron but not sure what each of the coloured dots represent.
Is the black dot standard lie/length? Which dot is for slightly flatter/normal length? Many thanks.

Black is standard, can't remember off the top of my head the other colour combos.
Go to the ping website and they have a web-fit on the home page... choose your height etc and it will tell you the colour you need

If they are going cheap enough remember Ping clubs can be adjusted for loft lie post purchase.

green is 1 degree upright but jim p is spot on here (no pun intended) lol...

As long as the irons are geniune (with serial numbers) you can goto ping and have them adjusted for free

Tom - black is considered Pings standard lie , something around 61-62 deg for a 5 iron at a guess ?

as for standard length , this again will be according to Pings standard length which may not be the same as another manufacturers standard length - generally though somewhere around 38" for a 5 iron ?

from memory the colour codes go :

blue 1 deg up , green 2 deg up , white 3 deg up , silver 4 deg up

black - std

red 1 deg down , orange 2 deg down , gold 3 deg down , brown 4 deg down

website may I imagine clue you in more ? - I'm just going back on past memory from my mid 90s Ping days