Hot clothes and cool cash from abroad brighten Cubans' lives.  Against Havana's gray stucco-and concrete canvas, fashion-minded Cubans create splashes of unexpected color. Relatives send as much as 800 million dollars a year. "If I didn't get money from my daughter in Miami," says a Havana retiree, "I couldn't make it."  Disadvantaged in the stratified Cuban economy are those who rely on government stipends of food and pesos for survival