It's probably multiplying the colours. That's pretty typical for a parameter like this.

Each colour channel is interpreted as a value from 0 to 1, then multiplied with the corresponding colour channel of the tint colour. So:

_______________ times red (1, 0, 0) = white (1, 1, 1) = red (1, 0, 0) grey (0.5, 0.5, 0.5) = dark red (0.5, 0, 0) black (0, 0, 0) = black (0, 0, 0) 

Under this scheme, pure blue (0, 0, 1) tinted with pure red (1, 0, 0) will turn black. But if you use intermediate blue & red colours (ones with some non-zero values in the other two channels) you may get a dark purple.

It's probably multiplying the colours. That's pretty typical for a parameter like this.

Each colour channel is interpreted as a value from 0 to 1, then multiplied with the corresponding colour channel of the tint colour. So:

_______________ times red (1, 0, 0) = white (1, 1, 1) = red (1, 0, 0) grey (0.5, 0.5, 0.5) = dark red (0.5, 0, 0) black (0, 0, 0) = black (0, 0, 0) 

Under this scheme, pure blue (0, 0, 1) tinted with pure red (1, 0, 0) will turn black. But if you use intermediate blue & red colours (ones with some non-zero values in the other two channels) you may get a dark purple.

Here's an example of using "multiply" blending to tint colours, via this tutorial