Asymptotic Freedom A Colorful Story for Understanding the Strong Force Yong-Shi Wu Center for Advanced Study Tsinghua University (and University of Utah) (Colloquium on 2004 Nobel Prize ofAsymptotic Freedom -- A Colorful Story for Understanding the Strong Force Yong-Shi Wu Center for Advanced Study Tsinghua University (and University of Utah) (Colloquium on 2004 Nobel Prize of Physics)