It depends on the spectrum of blue light. Blue light promotes compact bushy growth, thickening of leaves etc, but if it is a very narrow spectrum of blue light it wont do very much for plant growth at all. It needs to be a broad spectrum of blue light. Without knowing the colour spectrum of your blue light its impossible to tell.
My light is mostly white LEDs, with some RGB LEDs that are for effect only. The blue LED
is such a narrow spectrum it doesnt promote plant growth at all. The white LEDs contains the broad spectrum of blue for plant growth. I know people with non planted tanks who only use the blue light setting, specifically because it doesnt promote algae growth.
For info, red light will promote long growth and spreading. Green light is useless to plants, so it just reflects the light away.