There isn't a lot of textual description regarding the garden in "Games at Twilight."  The main focus of the "nature" description is about the weather.  It is hot.  Really hot.  

Their faces were red and bloated with the effort, but their mother would not open the door, everything was still curtained and shuttered in a way that stifled the children, made them feel that their lungs were stuffed with cotton wool and their noses with dust and if they didn’t burst out into the light and see the sun and feel the air, they would choke.

Regardless of the heat, the children desperately want to be let outside in order to play. That's when the reader gets a brief description of the garden.  Between the veranda and the garden is a big white wall.  Hanging on the wall is a very colorful plant called a bougainvillea.  It's a pinkish purple flowering vine.  Big, sharp thorns too.  The garden itself is described as being colorful, but that is not due to the variety of flowers and plants.  The color comes from the stones and walkways that guide a visitor through the garden area.  

The garden outside was like a tray made of beaten brass, flattened out on the red gravel and the stony soil in all shades of metal—aluminum, tin, copper, and brass.

There are a few plants.  The text mentions some small shrubs and bushes.  There is a brief mention of a patch of grass in the garden, but it also emphasizes the dryness and the heat of the climate.  

 . . . stood for a moment in the center of the yellow lawn,   

All in all, it doesn't sound like a great, beautiful garden to play hide and seek in, but it doesn't matter.  The kids are desperate to do something other than sit inside in a hot, stagnant room.