Sale of which colour(s) of refrigrator registered the highest percentage increase between 2010 and 2011?

Percentage increase in red colour from 2010 to 2011 = $$\frac{45 - 30}{30} \times 100 = \frac{15}{30} \times 100 = 50$$%

Percentage increase in blue colour from 2010 to 2011 = $$\frac{48 - 32}{32} \times 100 = \frac{16}{32} \times 100 = 50$$%

Percentage increase in Lemon colour from 2010 to 2011 = $$\frac{32 - 23}{23} \times 100 = \frac{9}{23} \times 100 = 39.13$$%

Percentage increase in Grey colour from 2010 to 2011 = $$\frac{34 - 27}{27} \times 100 = \frac{7}{27} \times 100 = 25.92$$%

There is no increase from 2010 to 2011 in white colour.

Sales in red and blue colour registered highest percentage increase.

Hence, option C is the correct answer.