I'm following Glenn Fiedlers excellent Fix Your Timestep! tutorial to step my 2D game. The problem I'm facing is in the interpolation phase in the end.

My game has a Tween-function which lets me tween properties of my game entites. Properties such as scale, shear, position, color, rotation etc. Im curious of how I'd interpolate these values, since there's a lot of them. My first thought is to keep a previous value of every property (colorPrev, scalePrev etc.), and interpolate between those.

Is this the correct method? To interpolate my characters I use their velocity; renderPostion = position + (velocity * interpolation), but I cannot apply that to color for example.

So what is the desired method to interpolate various properties or a entity? Is there any rule of thumb to use?