Take a look at the blue paint.
This is not the works of some bored teenage vandals. It actually betrays somebody shoddy paint job.
There was probably something on the wall all these years and when HDB re-painted this place orange, the painter just painted around that object.
When I was little, I remember the round stairways were painted blue. It was a rather dull and depressing type of blue.
Fortunately, HDB got the colour right as I feel that Orange does make the estate look vibrant and cheery.
I hope the next colour change......if there is any.....would not be too "ORBIT".