I have material, that takes camera under my map and make it appear on material, so is there a way to make for example black and replace it with any other color? I need to make minimap, but i need to make all other color exept red to be invisible.
Use a LERP:
when the alpha-input is 0 it will be just the A input, when the alpha-input is 1, it will be the B input, weighted in between. eg: alpha of 0.5 will be 50/50. You can use values outside of 0 → 1 if you want and the appropriate input will be scaled (multiplied) appropriately. eg: if I scale the checker-pattern by 3:
0 (black) is still 0 and 1 becomes 3 which mucks up the texture.
This is one of the cheapest ops, use this vs IF if you can help it.
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Yeah, i see, but how can i replace only black color to be invisible? Is there a way do do such a thing? Or can i just somehow make that on my level “void” below my level would be just invisible insted of black?
Ah! So what you seemingly want more is maths to make a hard-edge?
The IF node can certainly work there, and it’s not ‘bad’ to use it, just that b/c both paths are evaluated, people tend to use it thinking ‘oh, that pixel will be black so the other path never fires’; no. You still have to account for the cost of either path b/c pixel-to-pixel you won’t really know if it will always be black. 
LERP, you tend to use as a weighted-blend, so it’s implicit that both paths need be evaluated anyways. 6 of one, half-a-dozen of the other, but with a subtle nuance.
What you really want is to know how to make a hard-mask.
IF is actually useful here, as well as Step:
The multiply-by-1 is just to show the gradient; 0 on the left progressing to 1 as we move right.
The IF cuts the alpha at 0.5 and blends only one or the other based on that pivot-value.
The way you read step is ‘if X is greater-than-or-equal-to Y, return 1, else return 0’. In this case it cuts the gradient at 0.25. I find Step tends to pack better overall, that in more complex materials, you tend to save instructions vs other methods.
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