When you do a tellraw command with a hoverEvent and you specify a color (such as specified below), the color only works along the first line.
When hovered, should show
Based on 1.11.2 decompiled using MCP 9.35 rc1
This happens because the method net.minecraft.client.gui.GuiScreen.handleComponentHover(ITextComponent, int, int) just splits the text at line breaks and then renders each line separately. Therefor the second line has no formatting anymore. Instead the method net.minecraft.client.gui.GuiUtilRenderComponents.splitText(ITextComponent, int, FontRenderer, boolean, boolean) could be used.