I thought the standard sidelights looked yellow compared to the dipped and main beam lights. Initially I bought some laser blue replacements (Halfords part number 501). Although they are rated at the same wattage (5W) the colour of the light was more white and looked better.
The blue coating deteriorated on the bulbs so I then decided to buy some LED replacements. These Superlux bulbs are the same size as the originals but have surface mounted LEDs which are supposed to give a 180 degree light pattern. I bought them from AceParts