You can definitely do that (and can do it in so many ways it's not even funny, in-between the color filters, gradients and fades).
Now, can you show me and go into the details of one of the many ways to do it?
Let's suppose I want to apply an overall orange filter.
Real quick & dirty way:
Start your project with the B&W image. (Assuming you already have a B&W image here, saving a step.)
Tap the adjustments icon (4th icon from the upper right) > Color Balance.
For an orange-like color, start with an RGB combo of around 90% 55% 25%. Tap the confirm icon.
You can get even more fancy-schmancy. e.g., You could duplicate the original B&W image, apply the orange color like before and then tap the More icon (looks like an ampersand "&") > Fade. You can then go to town with how the fade starts, ends, add stops, etc.
There is a misunderstanding here. My fault, I have not been able to explain what I need to do.
In fact, I wat to apply a color filter *prior* the BNW conversion, the same way we used to do with analogic film BNW photography with the aim to change the contrast (e.g. darken blue skyes against bright clouds, you know...).
I know for sure (because I extensively use it) that Snapseed has this option available during the BNW conversion procedure (green, yellow, orange and red filters).
I also know (but only from readings as I do not have the program) that PS CSx has a built-in way to do this as well, even in a much more sophisticated way.
What I am asking is if anyone here knows a way to accomplish this in PSTouch as well, so I could drop Snapseed and obtain a better quality image.
I hope it is clear now, I'm sorry for the misunderstanding.
Could you post a link or image to an example?
Ahh, so B&W conversions based upon color tone?
Hmm...the best way I can think of in PS Touch is to adjust the color like above and then do a straight Black and White command. (Adjustment > Black & White.) That's more trial and error than anything though, so I'd make a copy of the layer beforehand. : /
Since we can work with layers in PS Touch, we could composite different layers of B&W using fades; something to think about anyway.