make a new layer and choose the 300pixel brush and go over the posts you want and set it to overlay, or lighten or screen then delete parts you dont want colored,

in other words, well, my way.
i would make another layer,
then set it to lighten, then color
areas that are light colored [ex. white]
like with red bright green, etc.
&then just erase what you dont want colored,
then merge it.
basically everything ^^said, but yeah.
haha

You could also set the color layer to "color" or "hue." And gradients work beautifully.