Every business that raises on Seedrs has the option to opt out of the Secondary Market should they wish. We think it only fair that investors are made aware that the business they are investing in has done so. 

The green market symbol means the business can be bought and sold - opted-in.
The red market symbol means the business can not be bought and sold - opted-out.

Just because the businesses has opted into Secondary Market doesn't mean the business will be eligible however, that is subject to other conditions you can find out more about here.
Basically, if the share price of a company is about to change (for good or bad) and we are made aware, we will make the business ineligible until the price changes. Quite often we won't be able to divulge the reason/s why a share price will change.

Convertibles cannot be traded on the Secondary Market. However, if the convertibles are converted into shares in the underlying business, then those shares might be. This icon is to signify if the underlying business has opted to participate in the market or not and does not mean this instrument is tradable. Investors must wait until the shares (or ownership rights) are issued before they can be bought and sold.

Cohorts themselves cannot be traded on the Secondary Market. However quite often, as in the case of the EIS100 fund, cohort campaigns invest into Seedrs' businesses and those may be opted in to the Secondary Market.