Select/recolor antialiased shape?

[ramatsu]

I'm new to Affinity, trying to unlearn 30 years of Photoshop habits, so please bear with me....

I want to recolor an antialiased icon, currently black, to some other color, color X. The icon is alone on a layer, so the surrounding pixels are transparent. The 100% opaque black pixels to be 100% opaque color X, and each of the antialiasing pixels that are n% transparent black to become n% transparent color X.

In Photoshop, I would typically make a quick selection marquee around the whole icon, and use Cmd-Up, Cmd-Dn to nudge the image and quickly "lift" the icon pixels into a selection. Then I would recolor those to the desired transparencies described above by using Cmd-Del or  Cmd-Shift-Del depending on whether I wanted to change it to the current foreground or background colors. (Operating from memory on those keystrokes; it's been a while and I don't have PS to pull them from muscle memory, but if I'm off, hopefully you know the ones I mean.)

What method would I use in Affinity Photo to accomplish the same thing? Thanks!

(BTW - I tried Fill with Primary Color, but it turned all the antialiasing, n% transparent pixels, solid. So maybe I'm just missing whatever step it takes to get the pixels "lifted" into a selection the way nudging does in Photoshop, and then Fill with Primary Color would fill appropriately?) 

[walt.farrell]

Perhaps some of the ideas in this similar request will prove useful:

https://forum.affinity.serif.com/index.php?/topic/151152-replace-color-on-grayscale-image-with-clear-background/

[Lisbon]

34 minutes ago, ramatsu said:

(BTW - I tried Fill with Primary Color, but it turned all the antialiasing, n% transparent pixels, solid.) 

If i understood correctly I think, before you fill with a colour, you need to lock the transparency.

Try unchecking "Editable" on the composit alpha.

After filling with the colour turn Editable back on.

[ramatsu]

@walt.farrell: Thanks for the link, Lisbon's solution below looks like the ticket but there's a bunch of stuff to be learned from the rest of that thread.

@Lisbon: Perfect, that's exactly what I needed! 

I can tell there's going to be a long learning curve here, AP seems to have some very different concepts about pixel handling from PS. 

[Lisbon]

Glad i could help @ramatsu

[lacerto]

Here are yet other two ways to change the color of a pixel layer with antialiased edges, retaining semitransparent pixels, one non-destructive (Color Overlay Fx), and another destructive (use Paint Brush protecting the Alpha):