All with one filter

Oded-Dror , Try like

return //change return

Calculate (SalesAmit,

'Product'[Color] ="Red")

or

return //change return

Calculate (SalesAmit,

filter(all('Product'[Color] ) , 'Product'[Color] ="Red")

if you do not want other dimensions to work use all(sales) also

Oded-Dror the underline problem with your dax measure is that you cannot have apply filter when you have value stored in the VAR, in other words, salesamt you have stored in var is not getting filtered for the color ="Red"

SalesAmt Measure = SUMX(Sales, Sales[Quantity] * Sales[Net Price])

Total Sales Fix Red =
Calculate ([SalesAmt Measure],
'Product'[Color] ="Red"
//filter(all('Product'[Color] ) , 'Product'[Color] ="Red")
)

Oded-Dror  what do you mean responding to slicer? What slicer you are referring to? Are you slicing on the color?

Oded-Dror if you are filtering product color then then remove the filters and then apply the one you need.

Total Sales Fix Red =
Calculate (SUMX ( Sales, Sales[Quantity] * Sales[Net Price] ),
REMOVEFILTERS ( 'Product' ),
'Product'[Color] ="Red")

Oded-Dror awesome, my recent measure should have fixed that too, the measure you used, and it has one drawback, if you filter on any other attribute of the product, you will run into the same issue, let's product name or code or whatever, since you are only removing the filter from color, anyhow, it all depends on your use case, how flexible/scalable solution you want to develop. 

In the end, you have what you need that's what matters. Cheers!!