You can create a pixel selection using colour, tonal or transparency (alpha/opacity) ranges from your image.
If you decide to create a selection based on any range, your image is analysed and all pixels which fall into the chosen range are included in the selection. Pixels which are not in the chosen range are excluded.
Colour, tonal and transparency range selections are available from the Commands menu. These include:
From the Select Hue Range sub-menu:
Select reds
Select blues
Select greens
From the Select Tonal Range sub-menu:
Select shadows
Select midtones
Select highlights
From the Select Transparency Range sub-menu:
Select opaque—only pixels that are 0% transparent are selected.
Select partially transparent—all pixels with a transparency higher than 0% are selected.
Select transparent—only pixels which have a transparency of 100% are selected.