why do lady soul(after death) always wear white clothes?  

to make you wet ur bed ...lol

Probably they can't afford to dye

they don't always wear white. the one i seen a few times (my sister too) either wore black or was a black spirit. she wore a last turn of the century bustle dress. here is a gif i made to resemble her. she wore her hair not so fluffy at all though and might have worn a hat. i would only see her momentarily in bright daylight. long enough to see her wearing a bustle dress and she would be gone.

its our indian tradition...

I think after death There are no coloures of life. and thats why they wear white dress. and just for fun that they just don't want to waste colour.