WOW

Do you mean WOM? :-)

The ratio of total back amount offered for the selection to the sum of the total back and lay amounts. Example: 200 EUR are offered at back prices, and 1000 EUR - at lay prices. The WOM will be 200/(200+1000) = 0.17

So the blue color (and the value less than 0.5) means the back amount is less than the lay one.