final static String[] fgProposals = { "A", "B" }; 
final static String[] fgInfo = { "<font color='red'>A_info</font>", "B_info" };

@Override
public List<ICompletionProposal>
computeCompletionProposals(ContentAssistInvocationContext context, IProgressMonitor monitor) {
  ICompletionProposal[] result = new ICompletionProposal[fgProposals.length];
  for (int i= 0; i < fgProposals.length; i++) {
    IContextInformation info = new ContextInformation("AA", "BB");
    result[i]= new CompletionProposal(
        fgProposals[i], context.getInvocationOffset(), 0,
        fgProposals[i].length(), null, fgProposals[i],  
        info, fgInfo[i]);   
  }
  return Arrays.asList(result);
}