So we can use on http://asciimath.org a following text
color(red)(f(t))=color(blue)((a_0)/2 + sum_(n=1)^ooa_ncos((npit)/L)+sum_(n=1)^oo b_n\ sin((npit)/L))
to render a colored Image. Try it.
Is it realised in plantuml.jar? If yes, then option color can be ommited!
Thank you for your Support!