While the perception of color is culturally dependent, blue and white are known to be one of the most popular for logos and national flags. In India, the color white is particularly important for clothing. It is typical for male politicians or authoritative figures to wear all whites. Dhotis, always white in color, are essential for formal ceremonies and events too.
India is probably one of the most difficult countries to keep clothes white: colorful food, red pan (chewing tabaco/mouth refreshner), general dust along with the red soil mixed with sweat and body fat and what not. Perhaps this is why putting on spotless white clothes has extra significance.
The fabric whitener bottles are blue. Furthermore I heard that the whitener actually makes the white fabric slightly blue to create the visual effect of looking whiter. Blue seems to be the common color choice for soaps as well. Hand washing stations in restaurants and around toilets I encountered outside of Bangalore often had blue soaps.