With this particular bulb you get a cool white light. As for the brightness, this light bulb clocks in at 260 lumen.
From Amazon
Bell 6W T5 Halophosphor Mini Tube - 4000K, 225mm - Pack of 1 - 260 Lumens
Lamps 2U Direct
6 watt Cool White T5 Fluorescent Tube
swiftelectrical
Bell 6W T5 Halophosphor Mini Tube - 4000K, 225MM