Change latex header color theme

to avoid Ubuntu ci error

! Package xcolor Error: Undefined color `Blue'.

(macos and windows were fine with it).

slides/ai_for_risk_header.tex

@@ -1,7 +1,7 @@
 % See https://tex.stackexchange.com/questions/409500/option-clash-hyper-ref-colorlinks-and-transparent
 % for useful tips on clashes and what does and doesn't need to be explicitly loaded here
 \documentclass[aspectratio=169, xcolor=dvipsnames, hyperref={colorlinks}]{beamer}
-\usecolortheme[named=Blue]{structure}
+\usecolortheme[named=blue]{structure}
 \setbeamertemplate{itemize items}[circle]
 
 \usepackage{smartdiagram}