Purple, Lightblue and their blends are all RGB colors
Purple // FullForm
returns RGBColor[0.5
,0,0.5]
LightBlue//FullForm
returns RGBColor[0.87
,0.94,1]
and
Blend[{Purple,LightBlue},0.5]//FullForm
returns RGBColor[0.685
,0.47,0.75
]`
I hope this answers your question.