Global color is not refreshed when you change it with a formula, triggered in a global switch

I created a global switch named switch_c for change colors in fonts, shapes, etc.
Global color variable is named c_50 and have this formula $if(gv(switch_c)=1,#80ffffff,#80000000)$
If i set in shapes, text, etc... PAINT > color, the global variable c_50, when i change switch_c status, color in elements is not refreshed.
But if i use the formula $if(gv(switch_c)=1,#80ffffff,#80000000)$ directly in each element in PAINT > color, switch work fine and colors are refreshed.

I'm not sure if is relevant or usefull but i'm working in a xiaomi A1M1, whit Android 8.1.0

As far as I know, global variables are parsed & executed once when the wallpaper saved & applied. CMIIW

Hope this helps.