FRuntimeFloatCurve and FRuntimeVectorCurve can be used in blueprints.
But !!!
Why is this FRuntimeCurveLinearColor not set to be available for blueprints ?
Engine/Source/Runtime/Engine/Classes/Curves/CurveLinearColor.h
USTRUCT()
struct FRuntimeCurveLinearColor
{
GENERATED_USTRUCT_BODY()