fixed random background color generation in tiles0

[snlagr]

backgroundR, backgroundG and backgroundB are multiplied by 255 twice resulting in generating (almost) black color every time.

[leesaypeng]

backgroundR, backgroundG and backgroundB are multiplied by 255 twice resulting in generating (almost) black color every time.

i think only need to divided 255 one time only because divided 2 times the value too small