Let's start with the base versions of a dual land and a triland for comparison. Note that the name and type line are colorless for dual lands. Conversely, everything is gold on a triland, there's no distinction between different trilands other than in the rules text.
So far I've used the frame below, which puts dual colored stripes on a base blue land frame. You can see the name and type line are blue in this example, as is the text box.
Here's a number of variations on this theme, using either or both base frame as inspirations. First your suggestion, which works well for signaling blue, but you can't immediately divine which other colors it generates. The second example puts those secondary colors behind the rules text. The third example drops the golden name and type line from the second example in favor of the colorless name and type line used on duals.
The fourth example is a variation on the regular dual frame, replacing the colorless color on the name and type line with the blue from a basic blue frame. I personally don't think this one is particularly clear, but if you also make the pin stripes blue, you get the fifth and final example.