Add warning message for unrecognized toolbox colour value. (PR #1881)
Add warning message for unrecognized toolbox colour value. (PR #1881)

Fixes #1831 
rachel-fenichel/blockly,twodee/blockly,trinketapp/blockly,joshlory/blockly,rachel-fenichel/blockly,rachel-fenichel/blockly,joshlory/blockly,twodee/blockly,picklesrus/blockly,mark-friedman/blockly,rachel-fenichel/blockly,google/blockly,trinketapp/blockly,nickmain/blockly,twodee/blockly,twodee/blockly,google/blockly,picklesrus/blockly,google/blockly,twodee/blockly,google/blockly,rachel-fenichel/blockly,rachel-fenichel/blockly,mark-friedman/blockly,nickmain/blockly,nickmain/blockly,rachel-fenichel/blockly,google/blockly,nickmain/blockly,google/blockly,joshlory/blockly,nickmain/blockly,nickmain/blockly,twodee/blockly,picklesrus/blockly,mark-friedman/blockly,mark-friedman/blockly,mark-friedman/blockly,google/blockly,mark-friedman/blockly,trinketapp/blockly,trinketapp/blockly