No. The gray patches can probably be assumed to be uniform in IR, but the other patches are not designed to look any particular way. There might even be different versions of CCs which use different pigments, and while they look exactly identical in visible light, they differ in infrared. With less accurately colored things like flags, this is a rather common occurrence. After all, IR means completely different wavelengths that have nothing to do with the visible light - apart from a few tendencies that allow for some uncertain predictions.
Color IR pics are dichromatic, they differentiate “shallow IR” (from the cut-off wavelength of the filter to about 770nm - depending on the sensor) from “deeper IR” (any longer wavelength to the end of the sensitivity range of the sensor, which is around 1050nm). So a 680nm filter results in strong, a 720nm in more modest and a 760nm one in extremely faint colors, while a 850nm filter produces perfectly monochromatic results. With the WB set on a presumably uniform reflector (like a white wall), the shallow IR results in redder, while deep IR in bluer hues. The two extremes can be easily reproduced using red and IR LEDs, and I’m ready to do so.
But I think the tint range should be extended anyway, if it’s possible without adverse effects. It could be implemented as an option which can be enabled in the settings panel, and is disabled by default - so common users wouldn’t notice any change.
And what do you think about the “windowed” slider I described earlier?