Daniel Bernad

Sia and her son looked ready to color in the Three Little Pigs together ... matching as a pair of pink crayons while going Trick-or-Treating amid a vicious custody battle. The singer-songwriter took her one-year-old son, Somersault, around their Los Angeles neighborhood Friday ... and, the two…

No "Cheap Thrills" here ... Sia and her estranged husband Daniel Bernad have been ordered to enter a mediation session to try to hammer out the custody issues in their contentious divorce. We broke the news earlier this week -- Daniel's emergency request for full custody was shot down by a judge…