I don't like the Trillian's appearance so I emailed their customer service and told them I hate it.

"Hey, I prefer a simpler graphical layout, with no gradient of color.
From all the themes provided there, I can't pick a suitable one.
They're too complicated while I prefer something simple and nice.

Hope you take this seriously."

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Woo, they actually replied me.

"Thank you for your feedback. Have you tried the Trillian Cobalt skin? It's simpler with less use of gradient color. Preferences -> Skins to change skins."

Their service impressed me a lot.