Edited by Christine

First version - while I was doing sample, Margaret wrote it out for you. She's fast! :D

I wanted to add to what she wrote though, once you have selected the bloom (both Photoshop and PaintShopPro have magic wand), make sure to slightly feather the selection so that the edges are not harsh, unless that is the look you are going for!

My workflow:

Photoshop - Running Windows
Magic Wand - set to Tolerance of 35, hold shift key down while clicking to add to selection.
Any little straglers that are hard to click on - switch from magic wand to freehand selection tool, holding SHIFT key down, just lasso those brats into the selection.
Select > Feather > 5px

Ctrl-J to move bloom to it's own layer.

Click on background layer, then added: 2 Hue/Saturation Adjustment Layers

1st hue/sat layer, change blend mode to color. 2nd hue/sat layer, as you are adding this layer, change saturation to -100 (slide all the way to left).
Go back to 1st hue/sat layer - double-click on left box in layer palette, make sure PREVIEW is checked, use slider on the HUE and start slowly sliding to the left.
(This will be individual preference as to how much - I used for this bloom ALL the way to left)

What those 2 Hue/Sat layers do - is give you a non-destructive way to change color to b&w, while still allowing tonal changes.

I then clicked on the TOP bloom layer - and brought opacity down to 71% (again, this is individual preference).

Have fun!